I've liked the Firefox browser ever since I found out about it a good while back. For one reason or another, from time to time I'd revert back to Internet Explorer because of some feature that I'd become accustomed to in IE that either didn't exist didn't work quite right in Firefox.
Firefox 1.5 eliminated a bug that was in prior versions - when you were browsing a website with frames, if you clicked on a link in one frame to render a page in another, the link that you clicked would not immediately change color to indicate you'd viewed that page. This is important in online forums that use frames, because this would be the visual indication of what messages you had and had not read. I learn alot by viewing messages online forums, so this was a big issue for me.
Another thing I liked in IE was the ability to right-click in a frame and choose Print, which would allow me to print the content that was only in that frame. Again, this was important to me because when I find a forum message I'd like, I wanted to print just it and not all the superfluous stuff outside the frame. I recently discovered in Firefox that you can Right-Click inside a frame and choose This Frame and then choose Open Frame in New Tab. Once the frame is rendered in a new tab, you can then print the content that was just in that frame as you would anything else. This may have been there for a while and I never noticed it.
Another thing that I couldn't do in Firefox was to be able to use Outlook Web Access to check my office email and also check for updates at Microsoft's windows updates site. These sites wouldn't work correctly in Firefox, so I'd have to fire up IE for them. Well today, I found out about a nifty extension for Firefox called IE Tab that allows you to run an instance of IE in the browser. Within its options, you can specify which websites you want to use the embedded instance of IE with. with Outlook Web Access, when you click on a message to view it, it opens in another tab rather than pop up a new window. Love it! And if you're a web developer and are viewing a page rendered in Firefox, with this extension you can right click a page in IE and choose View Page in IE Tab to see how a page would render within IE.
Another extension I've been using with Firefox is Sage. This is an RSS reader for Firefox. I've been using it for about a month and a half now and it works well enough for me.
I think most of my gripes with Firefox have been addressed, so it is getting pretty rare that I need to fire up IE itself. Oh, yeah. If you don't have Firefox and would like to try it, you can get it here.