Not to start a browser war, but Chrome has been updated again, I prefer Iron over Chrome (it takes Chrome and removes the Google snooping) and The latest Opera 10 Alpha 1 is the first browser to hit 100 on the Acid3 tests.
I like Fx better, and a new reason was just pushed to me - with Fx's profiles, which I keep on a separate disk, I can always install Fx in a new install, run it with the -ProfileManager switch and force it to use my profiles on a separate disk - which helps with me not having to friggin install everything again from scratch. (Mozillians, never fear, I perform a fresh from scratch install ever six months just in case). However, with Opera, you have to run it the first time, and then you can setup the profile in a different directory. Sure, it has a commandline option to *load* a different profile, but with Fx I don't need to use a commandline option but once - because it loads a GUI to allow me to permanently set up a different profile, with location and name as I see fit.