I had been using DivX, but that's been giving me audio artifacts at the end of the file for some reason.

My new plan, which I learned from thingswithwings, is to make mp4s instead. These use the H.264 codec, which you already know is shiny. I recently learned that the way to keep them from being pixellated is to radically increase the bit rate. I'm working with a bit rate of 9000 for my most recent exports, and they look great.