I've been using it since some of the early betas. Its a great browser. Good tabbed browsing and it does a good job on websites.

Only thing it doesnt do, by design, is run ActiveX applets. So you'll still need to keep IE around for that.

There also is a public beta available of IE7. I've been playing with that as well and it looks pretty sweet. They've taken a lot of features from firefox and put it in.