I've been a Firefox user for years, though I recently had to download IE9 to debug my website and actually quite like it. It fits in with Windows 7 too, like each tab appearing as a seperate window in the Windows 7 bar-thing accross the bottom... that I don't know the name of...
Still, I'm loyal to the little orange critter now (for a start, when it sees a .docx file it just downloads it as a .docx file and doesn't try to be helpful and convert it to a .zip file... cheers Microsoft, that was really helpful!).