I was always the IE guy. I used to know everything about IE, and at that time, it was just what people used. When I got my own laptop however, I began experimenting with all kinds of different browsers. For a long period of time I used Chrome because of it's speed and the fact that I had quite a nice skin installed :)
Recently I've been using Opera though. I really love the shortcuts in Opera, I use the keyboard shortcuts a lot, but what appealed the most to me was the beautiful Speed Dial screen. I really liked the old speed dial in Chrome before they put in a Google search thing on it, and this is essentially a prettier version of that old one :)
One thing I do miss though is the ability to quickly recover closed tabs when the entire windows has been shut down as well as the non-existent synchronizing...