I have used Firefox for as long as I can remember, because Internet Explorer is always getting "exploited". If you watch some of the articles on msn, zdnet, etc.. You will see countless stories of Internet Explorer's flaws.
Firefox is faster, HIGHLY customizable, and overall just a better browser to use.
As you can see Here
(w3schools.com) Firefox is the most used browser on the net today.
You can see Here
(cnet.com) that even after looking deeply into Internet Explorer and Firefox, Firefox still comes on top and beats Internet Explorer in every round.
(mozilla.org) you can see all of the add-ons and different customizations there are for Firefox.