I love Firefox. The extensions which you can download and install provide it with a lot of functionality that makes it easier to use.

The only problem I've had is that I designed my sites using it. Then when I went to IE to check them everything was off. I had been trying to do most things using DIVS rather than TABLES and the two just didn't display things the same. I've since gone through and fixed things so they show up the same in both browsers.

I've been watching my stats and probably 90% of my visitors use IE.