OK, obviously I never use IE when I'm forced to use Windows, I always use Firefox.
I followed the excellent work of the Fire*/Phoenix group since 0.1, downloading each release/milestone, until I discovered Galeon and later Epiphany.
I love Epiphany - it's simple, GNOME HIG compliant (which is a good thing), but I've switched to Firefox (at work, at least) for some simple reasons: Firefox looks and feels like a fully feldged GNOME application (apart from the icons); Adblock, Sage, other plug-ins; identical interface to the browser I use in XP (damn, I mentioned it)!
Oh, and I love the Firefox icon/branding. Very cute. (By Hicks Design, who seem to have a good eye for design - kudos to them).