I used to use Firefox since it was called Phoenix 0.2 and switched over to Google Chrome when that came out. It is way better. Faster, more responsive, and much simpler to use. You won't believe how fast it launches and runs, both on my PIII machine and my C2D machine. Opera is a really good browser (although it takes some getting used to), and I used to recommend it on older hardware but with Chrome as good as it is it's hard for me to recommend it anymore, especially since Opera's interface is "wrong" on just about every platform. I like Safari also as it is pretty fast (though not Chrome fast) but it sucks on Windows (bloaty) and is still the best choice IMHO on OSX.
I never liked IE. As a web developer it is always the exception to the rule and all other browsers will render things the same as each other -- whereas IE does its own thing. As a user I find it clunky and overly annoying, with lack (until 7) of tabbed browsing and a clunky, dated feeling UI compared to the big alternatives like Firefox, Opera, Chrome and Safari.
I normally dislike using Windows very much for a variety of reasons but I use it far more often (all the time) now that I have Chrome (since Chrome isn't on Linux or OSX yet).
Chrome has really nailed it. It is so fast, so stable, and so responsive, that using any other browser feels like driving a Yugo. The user interface is simple and friendly, doesn't get in your way... EVER, and Chrome is just about everything I could ask for in a browser.