I use Opera. Sometimes IE6. Never FireFox. When I use a Mac, I use Safari.
I read an article once that Opera has the least security holes and it runs faster than the rest.
Actually I've recently switched over to IE. I reinstalled Windows Vista on here and I just didn't much feel like working with Firefox any more, so I just started using IE7 since it comes preinstalled with Vista.
Flat out Firefox wins the Blue Ribbon, gets the World Title, and subdues Internet Explorer in darkness. With its add ons, themes, and tweaking programs it by far out does IE in everyway including pop protection and an Ad Block there is no way IE will surpass. In fact IE is currently guilty of copying Firefox's Window Tabs, so