don't forget about extensions...
Another nice thing about Firefox is the fact that you can customize and enhance it by using extensions. Some of the extensions I use and can't live without:
Adblock Plus & Adblock Filterset.G Updater - Blocks out all web ads. Makes browsing much more enjoyable.
Auto Copy - Highlight some text on a web page and it automatically copies it to the clipboard for pasting elsewhere.
Forecastfox - Weather in the status bar of your browser.
DownThemAll - If you find a page with a bunch of things you'd like to download, DownThemAll can...well, download them all for you.
GoogleToolbar - I know, IE has one too, but I was just mentioning it.
PDF Download - Gives you the option of opening, or just saving a PDF file, instead of wondering if your browser has crashed while it chokes on a big file.
Tab Mix Plus - Adds tons of options to your tabbed browsing. Let's you restart the browser with all the same tabs that were open when you closed it. Reorder tabs, add close buttons to all your tabs, etc.
There are thousands more....All of these can be found here: https://addons.mozilla.org/extensions.php?app=firefox