I mostly use Firefox. I tried Chrome for a while, but early on at least when I tried to open a CCf thread in a new tab it would scroll to some random point in he page instead of the first new post. For a while I used both, but after Firefox added some of Chrome's nicer features I used Chrome less and less. (Back in version 3.4 or so my Firefox kept freezing when I first opened it, which forced me to rely on Chrome for a while though.) When I got my new laptop I didn't bother downloading Chrome on it. Also, some free software I downloaded to download streaming video claims to work on IE, Firefox, Chrome, Safari, etc, but in reality only works on IE and Firefox.
I tried IE a few times recently as was shocked at how slow it was.