I have had it for 1 week.
The installation took me at least 5 hours because I set it up in bridge mode+voip, but it is worth the time and money as I had a major issue with 7 other devices consuming the limited available bandwidth on Netflix, YouTube, downloads, etc.
Now the ping doesn't increase even by 1 ms while playing 3 Netflix streams, 2 YouTube videos, and running 2 torrent clients in the background... everything runs smoothly in 1080p without any lag.
Even when I was alone at home playing games, I had higher ping with my provider's router (50mbps OTE speedport plus) because the speedport doesn't prioritize network packets, whereas the edgerouter prioritizes based on application packets. This means that if you are playing games while streaming YouTube/Netflix on mobile devices/TVs and downloading on another device, the edgerouter will prioritize the game/voip (whether it's telephony, Discord, or video calls), then allocate the required speed to multimedia, and give the remaining bandwidth to downloads.
With a good access point, you will have a great network in your home.
After the basic setup, you can configure the SQM and hardware offload in 5 minutes and say goodbye to ping and bufferbloat forever.
I should note that in order to see accurate results, you need to put some effort into it because it prioritizes traffic only after "learning" your network, like artificial intelligence. I opened everything in my house to use the internet while I was playing, and it stabilized within 2 hours.

Edit: 4 months later, I have forgotten that I have it... I installed a mini UPS and it has been working flawlessly for 3 months without any interruptions. I found a way to prevent it from giving IP addresses to devices that I haven't granted access to, so that no one can steal from me. I also set up a multimedia caching server with an old external hard drive to avoid downloading the same movie from the internet every time on every device.

Edit: In January 2021, a major update was released that unified the device's firmware with UNMS. Now, future updates are done directly through the device's interface without having to search for files to upload, etc. (I think they are even done automatically at night). Somehow, Ubiquiti managed to provide the ability to control devices from other manufacturers through the edgerouter (tested with speedport plus/entry2i/h108ns). UNMS has made my life easier... I can control my entire home network from anywhere, see real-time activity, and receive notifications whenever a new device connects, etc. It has the capability for a permanent VPN, and for the average speeds in Greece today, its performance is sufficient to avoid throttling. I would recommend placing it on its side to ensure proper airflow and cooling because during periods of heavy usage, even with hardware offload, it does heat up a bit, not dangerously, but it's not cold either. The load balancing is the best for home networks with moderate connections. I have my DSL connection with excellent ping and stability but poor speeds, and a 4G modem with poor ping and stability but very good speeds, and the EdgeOS sends gaming voip, etc. through the stable DSL connection while downloads and other low-priority tasks go through 4G (all automatically... the edgerouter ran diagnostics automatically and detected the characteristics of each connection). The QoS automatically closes if it does not have ping critical traffic in order to have maximum speed, and when it detects packets from gaming, VoIP, etc., it opens and lowers speeds so that everything does not get stuck (for example, I let the computer download while I'm away and it reaches 6-7MB/s, but when I open a game and connect to a server, the speeds drop to 4.5, which is how I have it configured to avoid bufferbloat). A huge bravo to Ubiquiti for providing these capabilities in this "budget" gateway for free.

Update: I installed fiber optic in my house and before setting up the network, I decided to run some benchmarks. I connected the GPON terminal and behind it, I connected the Speedport Plus. I measured the speed and ping of the OTE gateway. Then, I set up my network with the EdgeRouter and ran the same tests. The ping was 2-3 ms lower and the speeds were 8-10 Mbps higher. I don't know why there is so much overhead in the Speedport, but the EdgeRouter doesn't have such issues. The differences may sound small, but don't forget that the above latency is for EACH frame. Additionally, on the EdgeRouter, I had traffic analysis and SQM enabled. I think it can handle the 100 Mbps I have even with VPN.

Update: I connected an EdgeRouter to a friend's ADSL line, and with the slightest network activity, even with SQM enabled and limited to 10 Mbps, the ping is completely unstable. It's not the EdgeRouter's fault; something has changed in the terminal equipment from the central office, and it seems that the frames lose their order when there is load (I have tested it on a fiber optic connection and VDSL without any issues). So, if you are on an ADSL connection, it may not help.

Update: I replaced the role of the router with pfSense on my server, and now the EdgeRouter works as a managed switch for 4 VLANs. Even though I load it with file transfers on almost every interface, it handles all 4 ports with 920-950 Mbps, and its CPU does not go above 70%. It likely offloads to a secondary processor, but still, the little monster shows its teeth in traffic. But don't forget that you can't escape TCP overhead with any miracle solution

We have a Cosmote VDSL 50 connection and the provider had given us the Speedport Plus. I didn't have any major issues, but during the quarantine period, problems started to arise due to increased usage. My partner's Zoom calls would freeze, the internet would drop in the mornings and the device needed to be restarted, and in the evenings, when using Netflix and doing some gaming on the smartphone simultaneously, the system would struggle, etc.

After doing some research, I decided to try the popular combination of Edgerouter Ex and Unify AP AC Lite. The Speedport Plus now only functions as a modem and for telephone services, while the rest is handled by the Ubiquity duo through PPPoE. I am completely satisfied for now. The configuration requires some work, but there are many guides available on the internet. No more freezing, low ping, stable speed on all devices. I find it positive that it can be upgraded by simply changing one of the two devices.

==5 months later==

Everything I wrote still holds true 100%. No more freezing, even when we have guests at home, two simultaneous Zoom calls work perfectly. In six months, I have only needed to restart it once on a hot day, whereas with the Speedport, it was almost every week. A very good investment, I would buy it again.