You do not need to have the FlashPlayer (or Gnash) installed in order to watch this video!

1. you need to allow cookies from youtube.com, at least "until the browser is closed"
2. you need to allow JavaScript from ytimg.com and youtube.com
3. visit http://www.youtube.com/html5 and click on the "Am HTML5-Test teilnehmen", the JavaScript will set a cookie
4. done

Note No1: Not all videos on youtube are already available as WebM/h.264, it is still a work in progress
Note No2: If you do not allow cookies "until they expire" but only "until the browser is closed", do not forget to visit that page to get a new cookie every time you restart you browser

Are there any other sites who abandoned the proprietary Flash videos, but expect some stuff to be done in order to work?