I am using Latest version 4 Mozilla Firefox Browser,It's very Stable and fast one...I have checked my speed using the browser,the uploading and downloading all fast.I checked my upload and download speed at Ip-details IE is not fast in page Loading,But firefox is best if you open more tabs also ,it won't get crashed,It has many addons.
Personally I like Chrome. It loads everything pretty fast. IE8 is rather slow at a lot of things. I'm a Web Developer, so I use Mozilla at work mostly because it has all sorts of development tools/addons. If you're looking for an something simple and fast I'd say go with Chrome.
I voted for firefox but this latest 6.0.2 version is really starting to bug me. So far it feels like it has a 50% fail rate at rendering sites properly. I'm constantly reloading pages here on Tom's, netflix, etc... seems like much more often lately. Chrome and IE are here for backup, but not quite fed up yet.