Finally! Boards came in a while ago from OSH Park (thanks to the nice folks there for some extra boards to replace just one broken one from the original batch) but I just got a little time to assemble the first.
The ATmega32U4 happily responds to my programmer so it seems like there's nothing in the way of getting some code on there.
The first order of business after checking basic functionality (LEDs and USB) will be to try flashing one of the ATtiny10s with a program that blinks its LED. With that proof of concept out of the way the more fun work of exposing all of the processors to the host can start.