I have been very excited to see the numbers on FireFox usage go up every week. Slowly but surely, FireFox has become the first real challenger to Microsoft's Internet Explorer since Netscape's heyday. There are several reasons why I think you should be using FireFox instead of Internet Explorer, but I'll limit myself to the top five. And I won't even mention security...
1) Tabbed browsing I really don't understand why Microsoft has left this out every iteration. It's very user-friendly and seems like it would be easy enough to implement, but for whatever reason they've yet to steal the idea.
2) It's faster It truly is, I've timed it. Even with a bunch of extensions (more on extensions in a moment), FireFox loads and browses significantly faster than IE. Dial-up users (you are still out there aren't you?) take note!
3) Extensions Extensions are little add-ons that developers create and make available for free on the FireFox website. Some of them like, Stumble!, Web Developer, ForeCastFox, and Sage, I can't imagine living without.
4) Bookmark handling Internet Explorer's "Organize Favorites" is and always has been a joke. How hard can it be to create an interface to organize a bunch of shortcuts? Apparently for Microsoft it's very difficult. As soon as you click on FireFox's "Manage Bookmarks" you'll smile. I guarantee it.
5) It's not Internet Explorer I'm not Microsoft bashing here, honestly. Any company that owns 96% of the market is going to get complacent. Microsoft was pretty complacent to begin with, so that kind of domination has been deadly for IE. Even if you never switch to FireFox you'll still be reaping the benefits of it down the road when Microsoft finally gets off its butt and does something good with Internet Explorer.
...but just to be safe, go download FireFox anyway http://www.mozilla.org/products/firefox/