Firefox is a superb open source browser, well worth a look, even if you think the browser you use at the moment is quite adequate.
Of the many advantages, probably one of the most important to Windows users is the fact that it's much more secure than Internet Explorer, reducing the amount of spyware etc. on your system. Other than that, Firefox is about the only browser about at the moment that is compliant with nearly all the standards for websites. So as a web developer, I'd prefer if you all used Firefox, because then I can be sure all my pages will display exactly as they were designed. It's also hugely customizable, with a huge array of plugins and skins that can make it look and work just the way you want it to.
Tabbed browsing is another strong feature, it may take you a while to get used to this concept, but basically you can have a whole load of web pages open in different tabs all in the same window instead of cluttering up your task bar with loads of minimised windows.
Mozilla are predicting that they will have a 10% share of the browser market by Christmas. This will be the biggest share of the web browser market owned by anyone other than Microsoft for many years. So if you haven't tried it yet, download it now, and help "take back the web", you should be impressed by the ease of use, and you will be able to see the web as it was designed!