I really, really dig this idea. There's a handful of little hardware projects I've wanted to do with an Arduino or the like, but I've found that if you've got slightly different peripheral requirements, it's difficult to find one of these boards that will fit the bill. The idea of being able to significantly change the functionality of the hardware pins without doing loads of work is fantastic.

One minor gripe would be higher precision DACs (only 8-bit?), though the ADCs look great. The DACs would be a problem for audio, though the ADCs would be good for the lab.