I found a funny bug recently when playing a video through the media player. Audio seems to be out of sync, but only only for videos with 6-channel AC-3 audio. All of the files that I play that have 2-channel AC-3, or DTS play fine. Normally I have my ATV set to pass audio through my TV to my receiver, but even with the optical audio going straight to my receiver, the problem still existed with videos with 6-channel AC-3 audio.
Not a big deal since I can convert the few video files I DL with 6-channel AC-3, but something to look into.