When I'm playing DVDs, they look and sound fine and play at the correct speed, but the time indication is wrong -- both the controller window and the on-screen time display show about half the correct elapsed time, and increase at about half real time. The skip functions behave similarly -- telling it to skip forward or backwards by 10 seconds skips about 20 seconds' worth, and so on.
However, MPEGs or AVIs on my HD are unaffected, and play back with the correct time display. I think this behaviour started around 0.8.0, but I'm not certain exactly which release. Still happening with 0.8.1. Mac OS X 10.2.8, PowerMac G4 2x500MHz.
As I said, playback is fine if you ignore the time display, so this isn't a major problem. But if you weren't aware of this issue, one more for the list?