I used to exclusively use Firefox due to the noted stability over IE. I had used IE up until 8, where the crash rate, combined with the security issues were just too much to handle.
Firefox introduced me to a whole bunch of add-ons such as Lazarus (which is the best fucking thing EVER) and some other tidbits. However, when I upgraded to Version 3, it just lagged really hard, and drained my laptop of too much processing power. It eventually reached a point where having MSN and Firefox open at the same time was impossible.
Of course, I still use Firefox today simply because of ChatZilla, which is probably the only client I can be bothered to use.
I tried Chrome, which I absolutely loved. The speed, the simplicity, the fact that Lazarus and Pastebin both have Chrome Extensions was just brilliant.
This, however, was icing on the cake.
Halfway through my Chrome-life, Umbreon Dan introduced me to Opera 10. It's almost as fast as Chrome, but it makes up by having more functions and features.
Nowadays, I use Chrome for anything long-term. I.e, Smogon and other things I have cookies stored on. Opera becomes my "links and random shit" browser, as well as the "catch-all" for something Chrome can't handle.
My recommendation; if your computer can handle it, go with Firefox. It's actually the most powerful, and a hell of a lot more reliable than people give credit for. However, if speed and simplicity is your thing, you really can't do better than Chrome.