I have had the phone for over two years, flawless in everything especially in photography, which I use it professionally as a photographer. The only downside is that a while ago I put it in water to take photos and from what they told me at the service, it got water everywhere and the motherboard burned. Unfortunately, I had to change some parts at the Samsung service and obviously even though they confirmed to me after the damage that it was checked and closed properly, it eventually got water. What can you say and what can you do? Does anyone know if I can hold Samsung responsible after the warranty expires for the phone getting water due to their mistake? I got the same phone again of course since it does the job perfectly. *Update that the second phone I bought slightly used, luckily with a one-year warranty from Samsung, had a problem with calls and with the internet completely lost through 4-5g. Although I was disappointed with the phone, at least through the warranty they will change the motherboard and we'll see!

So far, the mobile phone is excellent!
Perhaps one of the best devices still available today and will last even longer.
Excellent screen, impeccable speakers, perfect for calls, very fast without ever freezing on me, impeccable camera and video that suffer minimal quality loss at night.
The fingerprint sensor is not the fastest, but it works flawlessly for me!
Brightness of the screen under the sun on automatic is perfect.
I would say that the battery is also excellent! It has NEVER left me with heavy use throughout the day.
There are 1..2 useless things to disable and adjust that anyone can find on various forums without having to adjust resolution and hz that make the battery a beast.
I also provide a link and everyone can adjust it as they wish.
https://forum.xda-developers.com/t/samsung-galaxy-one-ui-optimization-guide.4376755/
Anyone who says they have phone crashes and overheating probably needs a Playstation and not a smartphone, otherwise they can get one of the new devices from 2022 that are excellent in everything and even fry them from the temperature!
Anyone who finds it used in excellent condition from 550 to 650 €, will be giving themselves a gift!

Personally, I use my phone for calls, social media, and photos...I'm just a regular user who doesn't use the full range of a flagship's capabilities, but at the same time, I choose it with high demands in the photography and video department, always within the limits of a mobile phone's sensors...

I will only refer to the photography aspect...

Under good lighting conditions, especially natural lighting, except for the excessive involvement of the software with overprocessing, the phone is really good...The top characteristic of its cameras is the versatility they have, giving truly endless possibilities in photos and videos...The automatic macro and the 100X zoom that are really noteworthy for a mobile phone "sell" well...Its portraits are equally good with very good standard features that save you from editing, always within the framework of click-post...Very good OIS even in 4K video...The 8K is oversharpened, so it is never used...

The selfie is really top-notch in photos and videos in any case...

Overall, I am really almost completely satisfied with the cameras under good lighting...

The drama begins under low lighting conditions where things, always speaking of a 1400 euro flagship, are simply garbage...Especially the video is for tears...Full graining, focusing weakness, and generally mobile phone video quality of 300 euros...Night mode is sympathetic and with the use of the expert raw application, tripod, and photographer's knowledge, you can take really noteworthy low light photos...Unfortunately, though, when you get a Samsung flagship, you have the expectation to take at least very good photos and videos with one click in low light, without wanting a three-month photography course and a private director...

Samsung's huge fault for me and a deterrent factor in buying the phone...

Personally, anything over 700-900 euros for this particular phone I consider simply wasted money...

Take a moment to read this educational text and you will laugh a lot at the same time, I promise you. Let me start with the basics. So, I found the Samsung Galaxy S21 Ultra 12/128GB in silver for 907€ with a free charger. I was initially happy about the price because it had a ~200€ difference. Normally, the device was priced at 1199€, if I remember correctly.

I opened the device and for 3 days, I couldn't find a single flaw, obviously due to excitement. However, because the phone is a tool for work for me and not just for show, after the first 3 days, I started noticing various strange things.

GPS: It frequently lost GPS signal. I googled it and saw that everyone has the same problem and it WILL be fixed with a firmware update. It is still being fixed.
PERFORMANCE: They don't bring their "good" processor, Snapdragon, here in Europe. I didn't have any issues with Exynos, but at such a high level, the difference is small, yet you pay for a premium device and the detail will make the difference.
BATTERY: It has a 5,000mAh battery that lasts about 5-6 hours of screen time with automatic brightness, and that's it. With a SIM card inside, data, Wi-Fi for 50% of the day, and with the signal in Greece, which all consume more battery than the tests you see on YouTube.

The cost of the device is 1000€+++ with the aforementioned problems. Mmm. Let's move on to the good things now.

One day, I noticed that the signal was constantly dropping and coming back at a crazy rate, as if it hadn't had its morning coffee. This continued throughout the day and the device reached 300 degrees, which made me afraid and I turned it off. I tried another SIM card, but it wasn't the issue. I did a factory reset, but it didn't work. All of this is already a hassle.

I called Samsung Greece, and after many discussions, they sent me to an official service center here in Athens. I took it there, they received it, and they will "notify me". After 3 days, they informed me that it couldn't be repaired, and Samsung issued an exception DOA. The store called me and explained that I have to go to their store, and since they no longer have a device to give me, they will refund the purchase amount. The 900€, remember at the beginning?

The charger costs around 15€, and the phone now costs 1024€. With simple math, one can find that I am required to pay +140€ +hassle +gasoline or tickets, as you wish +loss from the days that the damage has occurred and I couldn't work, and all of this without me being at fault for anything. The next person could be YOU, so pay attention to the following.

For Samsung, the giant company, it is PREFERABLE and BETTER to send a new device, issue a DOA, and put the customer who trusted them with a LOT of money, me, you, our neighbor, through procedures and hassle. I spoke with the responsible person at Samsung Greece, and he told me that this happens worldwide.

Result:
1. I have lost more than a week during which I lose money without this tool.
2. Samsung DOES NOT CARE AT ALL about its customers.
3. I have to go through procedures to get my money back and then buy something else or even the same thing with additional costs, without me being at fault.

Let's go again. WITHOUT ME BEING AT FAULT, IN THE 9TH MONTH with a device that costs 3 salaries, and they have no shame.

So, for those who respect themselves, never spend more than 800€ on a phone and stay away from SAMSUNG. In hindsight, I saw that everyone worldwide is criticizing them, especially now with the S22, they messed up.

Update 28/12/2022
Something happened that excited me after installing UI 5 (android 13). The battery life has significantly improved and it seems to not drain easily! Bravo for that alone! Now I would like an upgrade to the camera... Hopefully that will come too! Happy New Year to everyone!!

07/07/2022
It's been 5 months with the s21. I still have complaints about the 5000 mAh battery. With dark mode and automatic brightness and summer usage, it barely lasts a day. Unfortunately, it falls short of expectations. Huawei, where are you to step up your game here?
Photos: They are generally good, but Huawei's premium smartphones are unbeatable in terms of photography (opinion based on mate 20 pro, mate 40 pro, p30 Pro). I speak objectively, having used devices from almost all brands (Sony, Htc, LG, Samsung, Huawei, Oneplus, and briefly Xiaomi) with their top devices at the time. I can say that the Note 8 I had once may have had even better photos.
I apologize to Samsung supporters, but the reason reviews are written should be for "potential" objectivity in evaluating such a product, regardless of the brand. Thank you. END OF UPDATE 07/07/2022

So, I've had this phone for about a month now and I will compare it to the mate 40 Pro that I had until recently.
SCREEN-FINGERPRINT: The screen of the s21 ultra is indeed wonderful. Here, the mate 40 Pro falls behind, being slightly inferior without being bad, of course. The s21 has great blacks and contrast. After all, Samsung is renowned for that...
The fingerprint sensor works under certain conditions and sometimes causes concerns, while on the mate it works flawlessly.
SIZE - ONE-HANDED USE:
I have no problem using the Samsung with one hand (as it is slightly larger than the mate 40 Pro), but without a case, it slips a lot! On the other hand, the mate 40 Pro, although thicker on paper, was easier to hold and didn't slip as much, even without a case. Objectively, the mate was more beautiful than the s21 ultra, with more harmonious lines, also due to its almost 90° screen. Of course, the S21 is not bad... in short, the mate feels better in the hand.
CALL-AUDIO-CONNECTIVITY
Great call speaker, clear voice, weaker connectivity both with WiFi and data-signal. When I'm in, for example, an underground parking lot, it doesn't catch a signal like the mate 40 pro, which had strong reception and calls were clearer.
FUNCTION-SPEED: The s21 ultra is smoother in its usage, probably due to the genuine Google operating system and its services. The one UI 4 skin is great, with many options and a beautiful feel and speed. The Exynos processor is very fast for Samsung's operating system, and scrolling is smooth and trouble-free, but more power-hungry than Huawei's Kirin 9000. The truth is that Huawei suffered quite a bit from the lack of access to GMS. The mate 40 Pro would have been an even better phone, perhaps the best of all, if it could use GMS services! Firstly, the Kirin 9000, besides being very fast, could manage the energy of its much smaller battery (4400 compared to the s21 ultra's 5000) much better. The s21 ultra should last at least 2 days, if not 3, with such a large battery and a battery level of around 20-25%! The mate lasted the same amount of time, even with a smaller battery (definitely 1 and a half days). The same applies to the s21 ultra but with more attention to detail in its usage... In a few words, the Samsung one ui 4 is very good, the Exynos is fast but has poor battery management for its 5000mAh battery - quite power-hungry. On the other hand, the Kirin is excellent in energy management (it took 10-15 minutes for the battery of the Mate 40 Pro to drop from 100% to 99% - it didn't easily drop from 100%). On the Samsung, it drops IMMEDIATELY to 99%!!... a little strange. Where the Mate lacked was in the ease of use of Google services that it didn't have. Due to this fact, and having to deal with an imitation Android from Huawei, the Kirin would occasionally freeze and it was a bit annoying...

SOUND-MUSIC: The sound of the s21 ultra is slightly better than the Mate 40 Pro, probably more balanced... in no way does the s21 ultra have bad sound... on the contrary, it is also very good!

PHOTOS: (I don't have enough opinion on videos because I don't take many): Without having bad photos, the s21 ultra falls behind in colors and low-light situations, but excels in zoom compared to the Mate. The Mate 40 Pro was EXCELLENT!! Incredible photos day and night...

It is famous for its photography system at Huawei...

The s21 ultra lags behind in night shots!

(Selfies are fine on both phones - however, the s21 ultra has 40MP while the Mate only has 13MP)!

IN CONCLUSION, I am quite satisfied with the experience of the s21 ultra, having a wonderful display and a very nice user interface (and the EMUI of Huawei was not bad, it was beautiful but not as beautiful as Samsung's). Where Samsung lacks is in the management of SUCH A LARGE battery (the percentage drops relatively quickly). If the Mate had a 5000mAh battery, it would easily last 2.5-3 days!

Lastly, in photography, it is clearly inferior to the Mate 40 Pro, but it doesn't mean that the s21 doesn't take good photos...

PRICE: The s21 ultra is worth quite a bit at 900 euros (12/256 version)...

If you can find the Mate for 700 euros now, it's a steal for what it offers.

P.S.: The Mate is more "readable" than the s21 ultra...

Sorry for the long review, but I tried to convey my experience with these two amazing phones...

(I miss LG [former owner of 2 of their phones] in mobiles because it was a very innovative company in phones. Maybe that's what ultimately "ate" it, too much experimentation. Many of the "tricks" of their phones are used by both Samsung and Huawei...).

Excellent build & assembly quality with all the known features of the company (waterproof, wireless charging) and excellent finish. Bright screen logically the best on the market with 2K resolution and 120hz refresh rate. Cameras are among the best if not the best. Battery is great considering it has to support such a large 2K & 120hz screen.

On the negative side, it is relatively heavy and there are some unexpected "breaks" for this price range, possibly due to the variable Hz refresh rate (0-120) of the screen (LTPO function). It doesn't always appear, but it is particularly noticeable when the device "wakes up" and is idle. It may seem logical, but it is not correct. Samsung should permanently set it to 120Hz for us perfectionists. And here, in this price range, I want it to be excellent in everything and not have cutbacks without a MicroSD card slot.

In summary, the ultra-bright screen with the sophisticated construction, the many and good cameras are the strong points of the S21 Ultra, and the weak points are the lack of a MicroSD card, its weight and size for everyday use, especially with one hand, and the high cost of acquisition.

* Important note! Be careful when removing the factory screen protector, as apart from glass with liquid adhesive (with whatever question marks may exist), the fingerprint does not work well with other types of crystals. Be careful because with the use of masks, as the situation has become, the correct operation of the fingerprint is necessary and given for me. Otherwise, with face unlock, you will constantly have to take off and put on your mask to be recognized, and certainly when this happens so many times a day, it becomes at least tiring and annoying!

Well, good evening to everyone!
I am writing this review from the s21 ultra. I have had this particular phone for about 4 months now and have been using it for the past 3.5 months. The phone is the best there is and the best I have ever had. Below, I will write about my experience using it in all areas:

-Screen: Okay, it's the best on the market with top resolution and 144hz. The user experience is unreal and you feel ashamed to use a phone with a lower quality screen. The brightness and colors are very satisfying even during the day.

-Battery: I really don't know how some people say it doesn't last them throughout the day. I use it for gaming (a lot), social media, music, and the camera quite a bit. It easily lasts me a day with the usage I mentioned before. In the beginning, it's understandable that the battery life won't be great because it needs to "learn" your usage, so give it some time. When I first bought the phone, I didn't use it at all for about 2 weeks and now I don't have any problems at all. As for gaming, it's very satisfying compared to my previous device which drained the battery quickly during games.

-Camera: Okay, here words are unnecessary, just like with the screen. In daylight photos, the phone is AMAZING!! The photos it takes are incredible and you can't fully appreciate it until you have this phone. The countless settings it has can take your photos to another level, and the zoom is unreal, especially the 100x zoom which is like having a telescope. As for night shots, some people say the noise is annoying at an extreme level, I don't know what they're doing or concluding from that, but I can say it's pretty good, not perfect but good.

-Software: The software is SPOT ON!! Without any exaggeration, it runs everything perfectly, flawlessly, excellently, and unbelievably FAST. This applies to the camera, social media, gaming, etc. There's nothing else to write because it's simply FAST.

-Sound: The speakers are much better than I thought, the sound is powerful and clear. Of course, it's not perfect but you can't say it's bad. I have no complaints about the sound EXCEPT that sometimes I can't hear the other person clearly when I'm on a call.

-Temperature: Some have complained about the temperature and how it rises to a worrying point, which I haven't noticed so far with gaming, where it would be a problem. There might have been an issue with the initial updates and then it got resolved, but personally, I haven't faced any problems.

-Price: Okay, EXTREME!! It's unimaginable to have a phone priced over 1000€, it's WAY TOO MUCH. I can say that the price could be around 700-850€ but not over 1000€, come on guys.

-Weight: I also read some comments about its weight. You don't buy a 1000€ phone without looking at its specifications, including its weight. I have to say that I have absolutely no problem with the size and weight, especially since I have put a case (Mobilfox) and protective cover for the cameras, plus a screen protector (I haven't found a decent glass protector yet, except for 1-2 which are very expensive). Other than that, the weight and size are something you get used to.

Conclusion: If you want to buy a mobile phone that will serve you PERFECTLY in EVERYTHING and last at least 3+ years in good condition, you should buy it with closed eyes. It is good at everything you do and will not disappoint you. These were my thoughts, and I hope I helped anyone who was considering buying it. If there is any "issue" that arises, I will update my review.