YouTube receives HTML5 1080p playback, testing new Flash features

Has anyone else huge problems with YouTube’s HTML5 player on the desktop? You can test it out if you activate it at <a href="http://youtube.com/html5" rel="nofollow">http://youtube.com/html5</a>. Be sure to watch a video without ads, only those will use the HTML5 player.<p>I’m running OS X Lion and Safari and I get stuttering video and awful performance. This doesn’t happen to me with any other HTML5 video player.

Does anyone have any links to 1080p videos that work with the HTML 5 player.<p>Here's one that only seems to work with the flash player <a href="http://www.youtube.com/watch?v=qb7zjKkLCoQ" rel="nofollow">http://www.youtube.com/watch?v=qb7zjKkLCoQ</a> (Glee - Rumour Has It)

This is the second article I see with these information. The 1080p playback is in for many months, though. Captions and annotations are newer, but also available for at least some weeks now.

So the only added feature is that it is in 1080p WebM / HTML5 combination? (Since H264/HTML5 1080p was already available)