Much is being made these days of "The Browser Wars". I think that's funny because I find some of my customers if asked "what browser do you use?" would probably reply "what is a browser?".
Internet Explorer is the browser that most everyone knows, mostly because it comes installed on every Windows machine. I switched to Firefox years ago because of all of the security issues with Internet Explorer. Firefox is still my browser of choice. I have tried the others, but see no reason to change. I see one reason NOT to change to Chrome, and that is their refusal to include something as simple as a left sidebar for listing all of your Favorites or Bookmarks. Why? I haven't a clue. I see no good reason to switch to Opera or Safari.
All browsers are free, and that is good.
Maximum PC recently published their review of these 5 browsers, with Firefox coming out as the winner. If you are at all interested, it is a good article, and can be found here:
Browser Battle 2011: Who Is the New King of the Web?
FYI, I have installed Firefox 4 on my 2 Windows XP machines. The install was fast and simple, and the differences are barely noticeable. You can read about these in the above-referenced Maximum PC article.