I have an Intel video card. Interestingly enough, I tried Ubuntu Jaunty right after it came out and I could not watch video pretty much at all. YouTube, Hulu, BBC News, even downloaded .avi's would play choppy. I finally uninstalled and ran Hardy for a bit, then went back to XP for a while.
Just yesterday I tried Mint 7/Gloria to see if the Jaunty problem manifested itself there as well. It does not. I can watch videos perfectly fine! There was an Intel video xorg update earlier today, but it worked fine even before that.
The only video glitch I had was that some .avi's would not play right in mplayer. The sound would be a few seconds off from the video. I installed VLC and now they play perfectly!