For people that have only tried Firefox for one day or something and shrugged it off as something that you don't need to switch over to, hear me out:
I'm probably like you. I hate having programs that overlap in functionality on my PC. So when someone wants you to install Firefox, you're probably reluctant because, you already have a browser, so why should you get another?
Aside from at least as fast or faster loading than IE and tabbed browsing, and the built in search, I find that Firefox's best advantage over other browsers is the insane amount of extensions. Extensions are user-created add-ons to Firefox. You can check out a list of them here:
http://texturizer.net/firefox/extensions/
Extensions *make* Firefox. They're just so damn useful. Examples of the ones I use include one that allows you to use 'mouse gestures'. What this means is, I can hold my right click down and drag the mouse around and it draws a line on my screen. If I draw a line to the left, the command = left, and I'll go back. If I draw it to the right, I can go forward in my history. You can do so much so easily, open new tabs, switch to next tab, close window, minimize, refresh, full screen...
Also I have "DownThemAll", which lists all links on a page, and you can download them all, or download certain ones (say of a particular extension, i.e. .mp3). Really useful, well for me
On that note I downloaded another extension that will automatically save certain filetypes to folders I specify, and even rename them or put them in subfolders if I like. So I can download all my mp3's to a certain folder, or subfolder, or I can download notes from school into their respective folders as well.
Or there's "BugMeNot", where if you stumble upon a website that requires registration to enter (i.e. New York Times), you can right click the username field and BugMeNot will provide you with a user-supplied l/p for the site. Ingenious.
And of course there's my GMail notifier that'll, well tell me whenever I get new GMail, I can also access my GMail with one click. Finally there's IEView for pages that aren't so compatible in Firefox but work well in IE.
I admit I didn't jump onto the extension bandwagon for quite a while, maybe a month after I installed Firefox. I just thought it'd be a hassle to look up and install them, but really it's a near one-click installation.
Go for it. Once you d/l your first extension, you'll d/l the rest like mad.
