Here's some input from an interested non-user of 60% keyboards. My first impressions:
1) The navigation cluster = superb
2) PBT by default = superb
3) Matte case instead of glossy = superb
4) Big, luscious space bar = superb
This is my favorite [theoretical] tiny keyboard yet.
Criticisms:
1) I think muscle memory is critical for use of the F-keys. Strike 1 against all tiny keyboards like this. If there is no space between the banks of 4, the user is forced to look, not feel. I can't say if there is a fix or not. Maybe I don't mind messing up the number row a bit by adding some spaces between them. (They might even be improved that way.) Or maybe different textures on the alternating banks. Color is not enough, but maybe rough vs smooth is the secret solution.
2) I think it is possible that Delete would be best placed somewhere above the enter key, because that is the level of a Delete key on a standard keyboard. Placing it by shift IS a good idea for the touch typist's pinky. But I am very curious to know the result of user tests with Delete in this position, compared to at the right of a smaller "\", compared to at the right of a smaller Backspace. To the right of the backspace might confuse the muscle memory, and I see that fitting it right of "\" is a problem to solve.
3) Any value the Windows key has on a keyboard like this is going to be less than the Fn key, right? Wouldn't it make sense then to fit a second Fn key on the right-hand side of the keyboard, even at the expense of further hurting (or annihilating) the remaining Windows key? I wouldn't miss the Windows key even if it just meant getting a bigger Ctrl key in its place.
Food for thought: Matias' 60% keyboard layout, but with a second Fn replacing the Delete key. Do you feast? If so, then where to put the delete function would be an open question.
My final first impressions for the record:
1) PrtScn, ScrLk, and Pause might be justified sitting on the lower arrow keys by their buddies PgUp PgDn.
2) Keys with 3 functions look like a mess to me, and I honestly start to wonder how to activate which function. Having no multi-color legends like on a laptop makes it worse. And having 4+ characters makes it even worse still. ") F10 0" is bad enough, but "{ print screen ]"? I almost wonder if the best solution here is taking advantage of the smaller Matias ALPS switches/caps and putting another function bar on top. 60% purists would protest, but they've also never had the chance to take advantage of compact Matias ALPS... until now. I'm not biased for any team, I just know that keyboards aren't done evolving yet. There might be a better way than HHKB.