The writer/director of "The Brothers Bloom" released an mp3 commentary track. What the hell, with free admission it seemed worth a try: so we cued up our mp3 players to the "hit pause now..." position, went back to the State theater for a 7:30 show, and pressed play together at the designated time.
The synchronization was off. I swear we'd followed instructions, but the commentary lagged by enough to make "now, in this shot..." hard to follow. I think I managed to correct that, but it took a long time.
He was really interesting. There wasn't much that made the movie itself more interesting--a lot of it (choices of camera placement, color themes, etc.) affects your experience of the movie without needing to noticed--but that stuff's still neat.
A DVD commentary track is an entirely separate sound track, so they can fade in and out the movie's sound separately. But with this the relative level of the movie and the commentary wasn't always good. And there were times when my brain would fight to listen to both, and get confused.