According to what I've been reading, IE9 is about the fastest browswer out there. The biggest drawback for IE9 is that it is written in a way that add-ons and extensions are very difficult to write. So you won't find a good free ad blocker out there, the ones that work are going to cost you a few bucks. I recently bought "simple ad blocker" for IE9, it wasn't expensive, and it really does work. The equivalent ad blockers for Chrome and Firefox are free, though (Adblock and Adblock Plus respectively).
So I have to agree that with IE9, Internet Explorer has caught up speed-wise with Firefox and Chrome, and passed them, but it still is at a disadvantage for add-on's. If you don't care about blocking ads, or don't use add-ons, then IE9 is a good choice, otherwise Chrome and Firefox 4 are both pretty fast, too.
So at home, I use either Chrome or IE9...Chrome primarily, and sometimes IE9 if needed to open a specific web page, use a particular player, etc. I use Firefox at work, primarily because I always have more than 15 tabs open, and Chrome and IE9 don't have any reasonable way of helping me to figure out which tab is which when only one or two letters of the name of what's running in the tab are showing on the the tab in the tab bar itself.