Well, I installed Firefox and don't see much difference, except that it is slightly faster - but then, I don't have many problems with IE's speed.
It lets you pick a pretty design, which is nice but ultimately too distracting. Once I'm viewing a web page, that's all I want to see. No other designs in the background.
It actually doesn't work well for me, because I use a personal portal that I store on my hard drive, and it can't load pages from that for some reason. I think I just need to change some code and it will work, but until I have/make time to do that... but I will at some point, because I love that it's open source and much more concerned with the user than with profits.
Anyway, now I'm interested to try Chrome...