What's gotten me interested in FF lately is the F11 fullscreen thing. When I do it in IE I lose the address bar (haven't used IE7), but FF keeps the address bar. Makes it so I don't have to exit fullscreen just to type in some site's address.
Just for the added space... otherwise the screen is just too cramped and hurts my mind.
VVVVVVVVVVVVVVVVV
Firefox, its much faster and I love the extensions but I find all the themes ugly, don't know why. Thinking about trying out Opera 9.1...tried reverting back to IE 7 in the past few days but its just too slow!