I've been running the released version of Internet Explorer 7 since it was released, and I downloaded Firefox 2.0 yesterday. If IE 7 had blown me away, I was going to de-install Firefox. I've used Firefox since its early days, due to its speed and tabbed UI. But I keep IE around because some sites don't work well -- or even function -- with Firefox. I was amenable to going back to IE because I find it a bit of a pain to switch back and forth.
But, unfortunately, while IE 7 certainly got into the general ballpark of Firefox, it didn't blow by it. And, at least for me, IE 7 loads incredibly slowly, while Firefox 2.0 got even zippier. So I'll continue to lead a schizophrenic existence. (I'm still futzing around with which Firefox theme to use -- I used Qute in the past, but it doesn't work with 2.0. The theme Mostly Crystal leads at the moment.)