I've been thinking about these as a way to set up a more ergonomic desktop area. Instead of keeping my arms up and in front, I could just have them lying off to my sides while I type. It also frees up center space for a lot of other things, which is the particularly important trait given how many input devices I'd be dealing with, ALL of which I want within ergonomic reach.
I'd probably have to give up buckling springs in the process (unless I luck out and find one of those rare Model M15/13H6689s at a price I can afford), though, and I haven't had the chance to try any form of Cherry MX keyswitch to know what I'd like (though based on descriptions, I'd probably go for Blues or at least Browns if I can; most of the ones I know of use Blacks).
Most of the split keyboards I've seen are rather flat like conventional keyboards for each half (Model M15 included), but I know that one of you basically cut a Kinesis Advantage in half and reworked the whole thing to act like a split keyboard. (I'd especially like to see a three-piece Maltron with the center numpad being the third piece, but given that those are even more expensive than the Kinesis Advantage boards...)
Any advice here? I know I've seen more than a few here, but haven't noticed a dedicated thread for them (especially if they're lumped in with single-piece ergonomic keyboards like Microsoft's old Natural Keyboard).