If you ever fancy trying out the latest version of the YouTube Player, you can visit “Cosmic Panda”.
http://www.youtube.com/cosmicpanda

If you ever want to ever change back, just visit the page again and click the button to revert back to the original.
Note: It only affects the browser you select it in.

Tried it for a few months – was okay but I still prefer the original.

P.S. YouTube has changed their homepage today. Love it or hate it, change was due to happen.