I love Firefox. I use it on all my PCs, with the only exception being my Mac, which uses Safari. I couldn't go back to surfing the web without the AdBlock Plus extension. I haven't seen an Ad on the web since I installed it almost a year back, and that's not something I'm willing to give up lightly! Also, being able to control iTunes with FoxyTunes is a nice little time saver! Extensions are where Firefox shines.
Then there's the built-in spell checker..
Ed