Well, my dev box is running memory tests , so I decided to take a crack at putting one of these together. The parts box provided everything but sufficient switches, so tried one of these instead. It worked well enough to verify functionality, but the buttons were problematical at best, the LEDs had the wrong common pin, and the entire thing was a bit flakey. Since I Need more switches anyway, I've placed an order for those. Thanks to those who contribute the writeup.
I'd really rather use a Uno than a Leonardo, but the code doesn't compile and I think it' sufficiently unlikely that the leonardo version will work to bother trying it. Please let me know if that's wrong. The Arduboy2 library doesn't seem to be any better off. At one point Scott had a branch of the Arduboy library for the atmega328p, but the examples in that don't build for me.
So, is the idea of moving from the Leonardo to a Uno dead? My next choice would be a pro mini (I buy those in six-packs), but that's still got a 328 and not a 32u4, so probably no better.