I'm in YouTube HTML5 trial, and the experience is terrible with Safari.
Every video is lagging severely, and the browser gets unresponsive constantly.
I have zero problems with the Flash version, and Chrome handles HTML5 YouTube just fine.
Activity Monitor says QTKitServer - Safari Web Content grabs more than 100% CPU.
Can I fix this?

I have 17-inch Mid 2010 MacBook Pro running Mac OS X Lion 10.7.2 with 8 GB of RAM.