I've been doing a non-scientific, one-commonsewer test of Mozilla's hot browser for about a year now. I like it. A lot.
I like it even better since MicroSoft has bloated Internet Explorer with downloads, hole plugs, and security measures rendering it a somewhat neutered, performance-less slug (remember your ancient 386?).
Although many users (not drug users) have drifted to Firefox out of fear of invasion through IE's flaws, that really isn't an issue for me because I have a miniature Israeli military presence at my firewall to discourage unwanted attacks.
With the exception of some government sites that aren't fully compatible, Firefox performs at least as well and generally better than IE. The controls and settings are easier to use than Internet Explorer as well.
To keep it simple I'm not going to do an in depth review as there are many available reviews online and Firefox has received the blessings of a plethora of techie magazines. Suffice it to say that my experimentation has evolved to the point where TWC uses Firefox 90% of the time. Is it perfect? Not quite, but it's on a whole higher level than the competition. I'm sold.
Full Disclosure: Nobody paid me to write this nor did I get any freebies as a result.