The USB module is mounted and working; uploads now possible using the megaCore version of optiboot, over the USB.  I was hoping the the RX/TX LED on the module would be visible even though it's mounted upside down, but it looks like it's mostly overpowered by the "power" LED that is also on the module.  the module fits really nicely against the board, and it seems like the way it is mounted will improve the physical robustness the way that I had hoped.

The USB Module could be slightly closer to the edge of the board; right now the board edge is almost exactly even with the micro-USB connector, while I'm used to having them jut out slightly.  OTOH, maybe this is good.

The 7805 footprint seems to be a little "short" for most of the regulators I have, and since I'm using the groundplane as a heatsink anyway, I don't see why the mounting hole shouldn't be plated through and shorted to the tab...  (ah; the tab isn't included in the  EAGLE package at all.)