Lots of people support FireFox, I've never used it extensively. My primary browser is Opera, it has worked fantastically for me. The key features common to both Opera and FireFox that make them better are tabs (ie, your taskbar doesn't fill up with lots of windows), control over popups, javascript, etc, and security. The other plus is that IE is the only browser condemned by multiple government agencies, including Homeland Security, as dangerous to use.