I have been looking through javascript performance videos quite a lot recently, not entirely applicable to this video, but one problem I see is that firebug are

I have been looking through javascript performance videos quite a lot recently, not entirely applicable to this video, but one problem I see is that firebug are great at profiling "userland" javascript, but there doesnt seem to be much information about how to measure the time spent in reflow and repaint, its basically guesswork of removing nodes from the dom / absolutely positioning thing etc.