Great, a browser war
Opera is my pick, and has been since version 3.xx. I'm currently using version 10 alpha, so quite a few years of use and so far no reasons to change. I have downloaded Firefox to see what the fuss is about and IE8 came with Windows 7, but I very rarely use them.
IE8 seems to be pretty much on par with the most recent Firefox. The little I've used it suggests it's pretty stable and works as advertised most of the time. If you're interested in it there's really no reason not to try it. The download is small, and you can always remove it if you're not satisfied.