I've had this keyboard for ~3 years and it's simply amazing. The key layout and superb wrist support made it my daily keyboard for everything, from office work to even gaming. It really made a big difference in comfort and typing speed. It will take a few hours to adapt to, but once you get used to it, it becomes irreplaceable. The batteries last insanely long "they're included". With heavy daily use and gaming, the batteries last about 1 year "no joke and no exaggeration". It's very responsive as well and having plenty of other radio devices "router, bluetooth, audio dongle" don't have any effect on its performance. Even for games, there's no latency at all. My old ergo K860 got damaged and several buttons stopped working after 3 years of intensive use, and I immediately bought this without second thought. It's expensive, but worth every penny. I also love how I can connect it to 3 devices and switch between them with a press of a button. It works with PCs, phones, tablets... via bluetooth or the included unifying dongle. Connecting it to the dongle can be done via the online interface: https://logiwebconnect.com/ .

Update: After a few months of use, things have improved. The keyboard seems to be durable and the wrist rest remains in good condition. The keys do not fade, I can type faster, and the feel of the keys remains the same.

Let's start with the negatives, which are also the most significant.

The layout is not the classic US ANSI, which, in my opinion, is more ergonomic and seems to be preferred by many other users, whether they are programmers or use it for professional purposes.
https://ultimatehackingkeyboard.com/blog/2015/09/09/ansi-or-iso-which-keyboard-layout-is-more-ergonomic

Because it is an ISO layout, the shift key is smaller and the enter key is in a different position and size, resulting in frequent typing errors.

Honestly, I don't know if I will get used to it. After 20 days, I can say that I am at 80-90%, but it seems that I will never fully adapt.

Also, the way the hands rest naturally, the "Y" key is always far away and requires the right hand to lift and stretch to press it. Maybe someone with particularly long fingers would not have the same problem. My hands are medium to large.

It is strange that, although it is slightly smaller than the Microsoft Natural Ergonomic 4000, it does not sit as well and needs to be positioned even further to the right on the desk, taking up more space than the mouse.

The letters are stickers instead of laser, so I expect them to wear off quickly.

Positives:

The keys have a relatively comfortable touch, better than the usual membrane keyboards.
It is convenient that it can be connected to 3 different Bluetooth devices and overall seems to be well-built.

Finally, at 125 euros, I consider it quite expensive, but if it had the ANSI layout, I would recommend it because nowadays, for some reason, you can only find ISO layout on the market.

1.

For a size comparison, I have placed it on top of the Microsoft Natural Ergonomic Keyboard 4000 to show how much more compact it is.

Very pleasant wristpad in terms of its tilt and the feel of the fabric.

The keys take a little time to get used to if you are coming from a keyboard with deep keys, because the distances here are shorter, but you gradually adapt to it.

The shorter length is convenient in relation to the mouse so that your hand doesn't stretch too much. It's just as much as needed.

Many of its buttons are customizable through Logitech Options. Quite a handy feature, as are the three buttons for connecting to different devices via bluetooth or usb.

The lack of backlighting I think helps a lot in terms of battery longevity along with the on/off switch.

I found it at a bargain price of 107 euros, but I would say it is worth its money even if it's a bit more.

The only negative remark I would make concerns the keyboard layout available in Greece. It is the US International (not just US) and, as you can see in the photo I uploaded, it has the vertical Enter and the small left Shift to accommodate the existence of two identical keys for the symbols \ |

Being used to the horizontal Enter and the large left Shift, this layout with the extra keys is a challenge. Especially when typing in Greek, they don't offer anything substantial. Note, these are not customizable through Logitech Options.

Personally, I could not get used to these two keys and I used the free software KeyTweak to respectively turn them into Enter and Shift (giving the unnecessary for me Print Screen the symbols \ | for when I need them) so that they don't hinder me while typing. I just mention this in case someone needs a solution for this issue.

I have been using ergonomic keyboards and mice for over 20 years. When it comes to mice, I have almost exclusively used Logitech products (such as the MX Master), while for ergonomic keyboards, I have always used Microsoft products (Natural Ergonomic Keyboard 4000, 7000, Sculpt Ergonomic, etc.). Overall, I was very satisfied with Microsoft's ergonomic keyboards, especially with the latest Sculpt Ergonomic Keyboard, which I have been using for the past 6 years (I even bought it for two different computers) and consider it one of the most comfortable and successful ergonomic keyboards. However, after 6 years of use, the fabric of the palm rest had lost its original texture due to friction and had become more "rubbery." Additionally, there was a known annoying issue with the small ESCAPE key and some malfunction with another letter key, which led me to look for a replacement after 6 years.

The options for ergonomic keyboards have been almost nonexistent all these years. Microsoft had the lead with quality and expensive products. But recently, Logitech introduced its own proposal, the ergonomic K860. Although I loved the Microsoft Sculpt Ergonomic keyboard, I decided not to buy another ergonomic keyboard from them (such as the Microsoft Surface Ergonomic Keyboard, which only comes in gray) due to Microsoft's idiosyncrasies (lack of support and drivers for Mac, lack of Bluetooth). Instead, I decided to give Logitech a chance, as I am completely satisfied with their mice.

The Logitech K860 is an expensive, high-quality ergonomic keyboard that, despite being a very fresh product, offers exactly what you would expect without any asterisks. Comparing it to the Microsoft Sculpt Ergonomic, which I have been using in recent years, it has several positives and improvements, as well as some negatives, which I will mention comparatively.

Starting with the positives:
(+) It is a full-sized black (or rather space gray) keyboard, larger than the Sculpt Ergonomic as it includes a full numeric keypad. It is not significantly larger or bulkier than regular keyboards (wireless or wired), but it is slightly larger due to the raised design that better supports the wrists, which slightly increases its volume (but not excessively).
(+) Its shape is a classic ergonomic design with a split keyboard (as shown in the photos), but Logitech claims to have conducted research on its ergonomic design, and I have noticed that when using it, my hands maintain a better natural posture compared to using Microsoft's keyboard, which I previously considered almost impossible. The difference is not significant, but given that it is a "taller" keyboard, the hands and wrists rest more naturally on it. This results in a comfortable usage that does not strain the wrists even after many hours.
(+) The fabric of the palm rest is completely different from that of Microsoft's keyboard. It has a smoother texture, does not easily get dirty, is even easier to clean, and gives the impression that it will last a long time (Logitech claims to have used three different materials and special coatings and paid special attention to its construction). Compared to the equivalent Microsoft product, it is clearly better considering that the latter would get dirty from dead skin cells and friction, losing its matte texture quickly and becoming annoying to clean constantly. It is not soft, but it gives you a more sturdy feeling, and in any case, it does its job and more.

(+) The connection to the computer is made either via Bluetooth or through Logitech's well-known proprietary USB unifying connector, to which you can simultaneously connect your mouse. This gives you greater freedom of choice, and there are also three selection buttons that allow you to connect the keyboard to three different devices (even tablets and mobile phones), which you can switch between by pressing the corresponding button. In this area, Logitech is light years ahead of Microsoft. In combination with the Logitech Options program (for both Windows and Mac), Logitech allows you to use and customize the keyboard as you wish, regardless of the type of computer, just like with their mice, unlike Microsoft's limited customization approach.

(+) The keyboard takes two small batteries (included in the package) that will last for at least a year.

(+) Very positive that the keyboard has an on/off switch for those who, like me, want to turn it off when not in use.

(+) It has some useful indicator lights, such as CAPS LOCK (very useful and one of the features I missed) and for the battery, as well as indicating which of the three devices you have set up is connected.

(+) The ESCAPE button is HUGE!!! Very convenient and user-friendly, a very smart move by Logitech.

(+) Plenty of buttons for secondary functions (media controls, shortcuts for brightness, computer lock, and many more), as well as a button that switches them to classic F1, F2, F3 functions with a single press. Finally, I can use all these functions on a Mac computer, something impossible with Microsoft products. The main function keys (Start, Alt) also indicate the corresponding Mac functions, cmd and opt.

(+) The keyboard has built-in adjustable feet to adjust the tilt according to each person's preference.

(+) The key response is excellent, and I did not notice any decrease in typing speed.

In any case, it is a very high-quality construction, where it is evident that Logitech has dedicated resources to its design and paid special attention to details in order to surpass the competition, particularly in the ergonomic keyboard market, where Microsoft used to dominate.

As for the negatives:
(-) The layout of the keys is not the classic US ANSI but the ISO, with the main problem being the left SHIFT key, which is smaller than usual.

(-) The only negative thing I noticed, only in comparison to the Microsoft Sculpt Ergonomic keyboard, is the feel of the keys. For some reason, I have the impression that my fingers slip more on the keys of the K860 compared to those of Microsoft. It is very likely that this is just my impression after years of using the Sculpt Keyboard, and over time, I will get used to it. It has not affected my typing speed or the mistakes I make, it just feels a little strange. In any case, I do not consider it a dealbreaker when it comes to purchasing it.
(-) The keys are not backlit, which did not bother me at all, considering that this keyboard is aimed at users who know touch typing, so they don't need to look at the keys anyway.
(-) The characters on the keys are not engraved but are stickers, which may affect their durability.

In conclusion, based on my short experience with the keyboard, I can say that at this moment it is overall the best ergonomic keyboard on the market. It is very high quality, comfortable, and ergonomic, with many useful functions that will satisfy even the most demanding user who knows touch typing and will tailor it to their needs. It has some negatives, but overall it offers more than any other ergonomic keyboard.

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UPDATE 15-4-2024: Almost three years of use later, I can say that this is a very good keyboard, comfortable, ergonomic, of excellent build quality, durable, with many customization options and connectivity to multiple devices (through the Logitech Options+ program), which will not disappoint anyone looking for an ergonomic keyboard. Indeed, after a while, the feeling of the keys becomes familiar and does not create any problems. No character has come off, and everything works perfectly, just like the first day. The wrist rest pad is of EXCEPTIONAL quality, and I emphasize that. I have not noticed any wear or fading; it is easy to clean and very comfortable. I can truly say that it is one of the device's major strengths. The only negative aspect so far is the ISO layout of the keys and the small left shift key...