Well, I populated the circuit board tonight, soldered up all the components, tossed in some batteries, and flipped the switch!
And nothing happened.
After ten minutes or so poking at the traces with my multimeter, I discovered that I have one trace out of place leading into the power switch. Fortunately a simple jumper from one pin to another on the switch was able to fix the problem. And it worked!
I have to admit, this thing looks pretty damn good! Not too shabby for my first PCB layout and project. I think I started toying around with this design over a year ago, so it’s pretty cool to actually hold a real, physical, blinking thing in my hands.