I got four prototype boards back from MacroFab yesterday, and this morning I tested them out. They work great! Here's a pic of all of them hooked up and reading out together - a 16 channel scope!
And here's what it looks like on the screen. Note how nicely the two identical signals are aligned in time.
I want to fix one minor thing... the micro-USB connector should point towards the back of the board, so the JTAG connector of the board on the right is not in the way! This is useful for powering the boards independently.
Now I just have to work up the courage to hit the "go" button on the remaining 196 boards. :) Maybe tomorrow!