Someone else posted that a copied (not transcoded) DVD played video fine, but without sound. But the MPEG2 bitrates may vary. And I don't know about the video acceleration, but I think that would be of substantial help.

I'm still experimenting - one DVD even my mac had trouble with (in the portable drive I was using) did manage to play the video menu.

If nothing else is running, there should be enough processing power to play a DVD reasonably well.

I should try a VCD.