Firefox here. I tried Opera, and it was very good, but the adverts in the free version annoyed me. Firefox is excellent. It doesn't crash, it doesn't have all the vulnerabilities that IE has, and the tabs and customisable toolbars are very useful.
Minimized windows are a pin in the arse, because if you have about 8 sites open, you can't see what they all are, and they take up your whole taskbar. With FF, you can have lots of sites open, and only have one taskbar tab. Also, you can minimize everything at once if you want, rather than having to do each window on it's own. Firefox is the way to go.

I don't even have IE installed on my machine any more.