I've had the KA for a few days now, including two work days. My impressions so far:
− It's slightly smaller and a lot lighter than I had expected. Both are good news, because I transport it in my backpack to work and back.
− The key action feels very good. I haven't used a real mechanical keyboard in years and it's good to be back! The Cherry browns are just what I wanted, with a light touch, subtle tactile bump and an audible but unobtrusive sound. I know they aren't universally liked here and I don't have much that I could compare them to, but I really like them.
− The contoured keywells feel really excellent and fit my fingers very well. The outer keys on the number row are a little harder to reach than on flat keyboards, but that doesn't matter to me because I rarely use them; I strongly prefer using the numpad on layer 4 of the neo layout. The extra bottom row is nice and very easy to reach, but I haven't yet decided on what to put there.
− While it takes some time getting used to it, I really really like the columnar layout. Horizontal staggering is obsolete anti-ergonomic bull**** and should have been abandoned decades ago. This feels so much better!
− Like I expected, the thumb keys are indeed a little too high for my taste, but I think I can live with that. I might try out lowering them like adreamer suggested. I found a description of that modification here:
https://geekhack.org/index.php?topic=45635.0.
− The one thing I really don't like about this board is that the thumb clusters are too far away. When I just let my thumbs fall naturally on the keyboard, they are basically on the inner edge of the innermost thumb keys (space and backspace on the original Kinesis layout). That makes it hard to reach the other thumb keys. The middle ones (delete/enter) are ok, the lower corner keys (end/pgdown) are awkward to reach without moving my entire hand, and all other thumb keys can't be reached at all without moving the hand. That's quite disappointing to me; if they'd put the thumb clusters a little more towards me and towards the outer edges, they'd be much more comfortable to use. But even with the suboptimal placement, it's still better than having to move my hands and then hit the keys with my pinkies.
− Except for their position, I really like the thumb clusters. Having access to six keys on each thumb opens up a lot of possibilities and I really like how the different keycap heights make it possible to accurately press individual keys or to use different combos just with one thumb; especially the middle thumb keys and the two smaller keys right next to them are suitable for all kinds of combo madness
− The tenting angle feels sufficient to me, but a little more would have been even nicer. Somehow I feel that the companies building ergonomic keyboards aren't courageous enough in this regard.
− Unsurprisingly, the esc-/f-key row is really ****ty. I knew that before and don't care because I can remap esc and rarely use f-keys, but still I really wonder what the designers were thinking. Even if the keys were mechanical like on the Advantage2, their placement still makes them virtually unusable.
− One downside of the KA that I hadn't expected is that it doesn't seem possible to have a layout with AltGr and windows keys. Or maybe I just couldn't figure out how to do it yet. This isn't such a big problem when using neo (it just means not being able to lock the the fourth layer), but it would really piss me off if I would still be using the german QWERTZ, because AltGr is really important for programming with that layout and I do like having the windows keys when using windows at work. If any of you know how to have AltGr AND the win key, do speak up please
− Except for a few minutes of FTL and Open Arena, I haven't done any gaming on it yet. But so far I think that as long as the games support full customization of the keys, the KA might be very nice as a gaming keyboard. It puts more keys within easy reach than a standard keyboard, the columnar layout makes perfect sense for gaming (as it does for typing) and ergonomics are just as important for gaming as they are for typing.
− I really have to do a lot of thinking about how to adapt the neo layout to this keyboard. But that is such a complex subject that I'll write a seperate post or thread about it soon. So far, I've put shift on the middle thumb keys, mod3 on the ctrl keys, mod4 on end/pgdown, ctrl on home/pgup, enter on backspace and I swapped win and alt in order to make alt-tab more tolerable. But that is just my first experiment, I anticipate a lot of layout tinkering in the near future
All in all, my temporary verdict after the first few days is that the KA is far from perfect, but despite its shortcomings still one of the best ergo boards on the market and definitely the best keyboard I've ever used, by far.
I'll report back as soon as I have accumulated some longer term experience.