I'm using Chrome, because it's fastest and simple. Before that I was using Mozilla, but after I tried Chrome I rarely come back there. It's because Mozilla is slower and I have too many plugins installed, which slow it down even more, not to mention how much space do all the toolbars take. Oh an I love it when you open a new tab in Chrome you get the 9 'most visited' pages. I haven't used IE in years, except for 0once at my friend's house, and I see it's improved, but I still prefer chrome and Mozilla.
I also like Opera, but for some reason I don't use it much.