After finding that I'd neglected to include pull-up resistors on the SoundWing, I decided to check this board as well. Sure enough, no pull-ups were on board.
While probably electronically sound, this layout is a horrible mess of leads and vias, and I think it can be better. I probably will rework the whole thing (including changing the order of I/O connections between the two big chips) before I send this off to anyone.
EDIT: How much do you folks think this board will need pull-up resistors, anyway? This board is intended for use with a SoundWing (another project of mine), which will have them on board; I really can't think of any application that would happen without it. Some feedback on this question would be helpful.