Hi,
I’ve been having the same problem. The animation I created is a simple move of a picture from the left side of the screen to the right (simple position animation).
When playing back AE exported videos rendered at 1920×1080 (1080P, 29.97fps Dropframe, 6-10mbps, H264, Best settings) the animation looks jittery in both windows media player and quick time. It’s much worse in quick time because it seems like a whole bunch of frames were dropped. Scrubbing the time bar doesn’t really help either. This is weird since h264 is supposed to be really good in Quicktime for 640×480 videos.
The thing is if I play the video back on a HD plasma tv, it looks fine. The animation is perfectly clear and it doesn’t look like it does on the comp. I know this doesn’t help if you need to play your videos back on a computer for presentations. But if your goal is to play it back on a TV, then it should be fine.
Good luck.