I built one - I even wrote half of the ROM. (That's my brush with fame - sharing ROM space with the Woz in a Replica-1 )

Vince Briel is the designer, and the best place for info are his forums at http://www.brielcomputers.com/phpBB2/index.php

AppleFritter has some discussion, but much less than at Vince's site.

And it's fantastic! Great fun to build, expand, program etc.

Ken