I switched to FireFox back at about 0.8 and have never looked back. The Web Developer toolbar is amazing and there are many other useful ones depending on what you use your browser for. Tabs make life so much easier and the browser has intuitive functions such as the ability to right-click on a highlighted phrase and then search Google for it. I also have an extension that allows me to highlight a URL that isn't actually a hyperlink and then open it in a new tab, which again is as simple as right-clicking and selecting the option.
One thing that I think puts people off in these days of WinXP is the default look of FF. Now people are used to seeing a graphically-rich desktop, as Mac users have for years, the out-of-the-box look of FF is pretty awful. Thankfully there are loads of skins for it and installing one is just a matter of clicking on a special link. My personal favourite is Noia 2.0 (extreme). Now my FF is pretty, too