I would switch to Firefox if it had a zoom function. Because I use a 46" big screen as my monitor, I like being able to control the size of the pictures and videos displayed. Firefox only lets me increase the size of the font.
Trust me, trying to watch a YouTube clip this tiny is harder than it seems. My resolution is set to 1920x1080, and trying to watch a 300x500 clip... yuck! With IE7 I could (until recently) load up the clips and then zoom the whole page, video included. For some reason, YouTube doesn't like my IE any more, so I have to use Firefox with it. Doesn't mean I have to like it, though.