Nice. Bookmarked. I never liked how Youtube solved playlists. I like the URL pattern, because it makes it easy, to write a bookmarklet that turns all Youtube links on a page into a playlist. :)

Some room for improvement: Please add title attributes to the buttons. Also the loop-button is a bit confusing to me. Maybe standard icons as seen in many other players are easier to understand. It would be nice, to have the volume slider slideable.

Mixtube did a similar thing, but seems to be broken at the moment: http://mixtube.org/