On my laptop, here are my results (lower is better, your results my vary):
Safari 4: 128
Firefox 3.5: 233
IE 7: 1181
IE 7 is almost 10 X slower than Safari 4. With more and more sites building rich interfaces and AJAX driven interaction this can be a serious issue. Recently I was working on a redesign of some category navigation pages. The new interface used AJAX loaded content and multiple tabs to display content. It worked great under Firefox, IE 6, IE 8, Safari 3, Safari 4, but was painfully slow under IE 7. Slow enough that in deference to the high number of customers still using IE 7, and the potential sales loss, we had to remove much of the rich interface.
Friends don’t let friends use IE 7.