BTW, if people want to try the integrated YouTube player (no longer WIP), please take special care to install GOOD codecs! The best I could find for (not only) Windows 7 are these:
http://www.windows7codecs.com/(use "expert setup" in order to disable the probably unwanted browser add-on stuff that unfortunately also comes with it!)
I haven't tested them on XP or Vista, but it's supposed to also work fine there...