I use Chrome. I almost always have both Firefox and Chrome open. They both have different strengths for me so I use them both for different things.

I can't use Chrome to watch videos on youtube because the adblock on Chrome won't block the ads. =/ And I wasn't impressed with Chrome's journal log in thingy. I use Firefox's lj login to log into three different sites and five or six different accounts. But Chrome has the better manga reading extension by far.