I don't know if it was already posted here about this topic, my apologies if it was...
http://www.mydigitallife.info/2008/11/20/how-to-embed-and-play-720p-hd-high-definition-youtube-videos-fmt22-code-hack/ I actually like the Youtube's HD implementation better than that of Vimeo's. Somehow Vimeo's tends to pixelate the edges in the video. Renat