So, I've noticed there's a html5 testing page on youtube. It won't work in gecko based browsers (it's not ogg theora) but it works on fully updated fedora 12 using a webkitgtk based browser (e.g. midori or epiphany; chromium builds still don't support video tag and I don't know anything about the webkit version in qt). The difference is great. Although not everything works as with Flash based youtube, some basic functions like pausing, seeking and such are already working smooth. And what's best is that the implementation is fully opensource (sans usage of patent encumbered codecs), does not crash as often (maybe does not crash at all, but I haven't done any rigorous testing) as adobe flash does and eats about half of the CPU compared to flash and nothing in paused state (while flash still eats CPU even when the youtube video is paused). I just hope the implementations will keep going forward an will make it's way away from just one testing video to full implementation.
The HTML5 enabled video (i.e. you don't need any browser plugins enabled, but you'll need some gstreamer stuff from rpmfusion [gst-ffmpeg] if you're using webkitgtk): http://www.youtube.com/html5
and the same video using flash: http://www.youtube.com/watch?v=uofWfXOzX-g
Very quick update: I've just noticed that when you hover over the video previews in the columns on the right side of the page, the hovered video will play in fast speed. Neat.
And another quick update: Right-click on the video and you can download it! I cannot wait for the day this will be the youtube.