Firefox is a perfectly fine basic browser. In my experience, if you throw a boatload of plug-ins at it, it becomes a resource-hungry, unstable mess. A few select plug-ins are fine, but if you want a full-featured browser, Opera is where it's at.
Google Chrome is an okay browser. I've used it a bit, but it lacks the features Opera has that I use on a daily basis. I've experienced some inexplicable crashes w/ Chrome, even post-beta, so it definitely has a ways to go in terms of stability. Also, it's built on the same platform as Apple's Safari browser, which is well-known for serious exploits. I know the beta got reamed for lack of security, though I haven't seen much about the final version's security (or lack thereof).
Internet Explorer ... I can't stand it. There's a laundry list of reasons why I don't use IE and I'm too lazy to go through them all.
Safari ... Still the only browser on the market that makes IE look good.