I am still on IE7 but have FF and Chrome installed.
FF used to be my favorite. You will like it, especially if you get the Adblock Plus Add-on:http://adblockplus.org/en/
If I am going to work on somebody's system, installing FF is about the second thing I do.
If you suspect an issue with a WWW page while using FF, you can always try it in IE. Some QA/Developers think "if it works with IE, my work is done". I'm sorry - that does not work for me. Developers test their stuff with IE, maybe with FF, maybe with others. This is becoming less of a problem since alternative browsers are becoming more popular.
Some Microsoft pages (another is some Yahoo! pages) will only work "right" with IE (Windows Update for example). That is fine for the occasional times you need to IE it so you need to keep some kind of IE installed just in case.
Personally, I started using FF and said "Wow, this is great!". Then I started using Chrome and said "Wow, this is great!" Now I hardly ever use FF. The adjustment periods can be a little frustrating, but hang in there and you'll be glad you did.