Have you guys seen this?
http://metalab.at/wiki/MetaboardIt's pretty damn awesome!
- (Mostly) Arduino code compatible - use Arduino IDE to write and program. Not exactly clear what isn't compatible - I'm guessing the USB port uses the interrupt lines, so may use one of the hardware interrupt lines.
- No USB-> TTL converter! Bootloader has USB firmware - AtMega168 connects directly to USB port.
It's very close to arduino form factor, but I think the pin headers have been moved to the 0.1 in grid. No ISP headers.
They give a step-by-step procedure for the entries required to the arduino preference and board files to allow you to upload from within the IDE directly over USB. The USB bootloader is linked to at the obdev website for free.
Seems like it could be a great trade off of functionality/pins for the gain of native USB support.
They even provide a full single sided schematic and board file to make your own. I'm going to try making one this week.