I've been drooling over the open tab ever since the Kickstarter went up. I have many keyboards from my firmware hacking days, but one with a keywell is missing from my collection. Sadly can't afford it, but it'll remain on my wishlist, so whenever that changes, whenever I'll be able to afford one, I will get one.
I'm not sure it would replace my Keyboardio Model 100 (the thumb key on that is just so incredibly useful), but it's the closest thing I've seen so far.
Good luck!