edit: i used to use firefox a lot but recently i've been using safari and it's working way better for me. i tried Opera for a while too it wasn't half bad.
I use firefox. The only reason why I use it over Safari is the fact that it was the quick search engines shit on the top right, and you can make quick bookmarks with images.
1. Firefox is alot faster that IE
2.its alot safer and more secure
3.you can download very useful ad-ons
4.you can change the skin
5. FF is more customizable and has way more user options than IE
6. FF has built in spell check, and it can hyper link any word you highlight