Ive been using Firefox for about 8 months now. I use IE for one thing, filling out forms. And only because Google toolbar doesnt work for firefox yet (that auto fill feature on that toolbar kicks ass for what I do).
Tabbed browsing rocks because it keeps your taskbar clean and un-cluttered however, ALT-TAB which is a very heavily used feature on my keyboard has become useless. Perhaps there is a way to switch between tabs without the mouse, a hotkey, but I do not know it. I avoid the mouse and this is now one of the times I am forced to use the damn thing.
But, I havent bothered with IE for surfing since I got Firefox and wont ever go back. WHen I first started using it, a few plugins wouldnt work, but as each new version (pre 1.0) came out, more and more plugins were available for it and now there isnt anything (except google toolbar) that doesnt work.