Most of these keyboards based on the ErgoDox (and the ErgoDox itself) make the mistake of considering that the thumb is a finger positioned like the others. And the keys you're supposed to hit with your thumbs are just placed in a crazy way (totally non-ergonomic IMHO).
To me one of the rare person who really "got it" is "Jesse" (he's both here, on GeekHack and on Deskthority) with its "butterfly" keyboard.
That's one of the only split (and ergonomic) keyboard that takes into account the fact that the thumb's opposition-apposition makes it unlike any other finger.
Look at his "butterfy" keyboard here and how smartly the keys you're to hit with the thumbs are positionned:
As an owner of the ergodox, I appreciate the efforts and iteration here. Sadly, the ergonomics of most non-split keyboards are hardcoded to a magic number. With the ergodox, I currently have the halves about a foot apart and really enjoy typing that way. (I have also "tented" the halves in the past).
I agree that the ergodox is not perfect and the thumb clusters could be improved, I'm just not sold that the butterfly does that.
Here's an old post with my initial impressions of the ergodox [0]. I need to add an update, but I have since purchased a second unit for home and have been typing with the "Norman" layout since day 2.
(BTW, massdrop currently has the keyboard up for sale, but you need to act fast as there is only a day or so left)
There's also AcidFire's project¹, which starts off by lowering the ErgoDox thumb keys and moves on into a more flexible system.
Separately, I've very gradually been working on a personal project starting with slightly modified Kinesis keywells for the fingers. (I've been using Kinesis keyboard for 15 years and am mostly satisfied with the finger portion.) I use small SPI / I²C adapters on the keywells for flexible separation and positioning². I have still not found a thumb arrangement I'm happy with, though.
That's funny; while I really admire the butterfly design I don't really see it as addressing that specific complaint. It's still got the thumb keys in the same plane as the Ergodox, so as far as I can tell it shares the one minor complaint I have with the Ergodox.
The AcidFire Nexus design linked elsewhere in this thread attempts to address this by dropping the thumb clusters to a lower level, which looks like a really great idea. The only other design I've seen which addresses this problem is Oobly's: http://geekhack.org/index.php?topic=49721.0
To me one of the rare person who really "got it" is "Jesse" (he's both here, on GeekHack and on Deskthority) with its "butterfly" keyboard.
That's one of the only split (and ergonomic) keyboard that takes into account the fact that the thumb's opposition-apposition makes it unlike any other finger.
Look at his "butterfy" keyboard here and how smartly the keys you're to hit with the thumbs are positionned:
http://blog.fsck.com/2013/12/better-and-better-keyboards.htm...