I've been playing with IE 7 beta 1 since last night and I've got a few quick thoughts. First, I suspect this is really more like an "alpha" than a beta. Second, their tabbed browsing UI is pretty nice. It's discoverable, it's easy to learn, and they've solved the overflow problem very nicely (we should do that!) Third, this new toolbar arrangement is going to take a _lot_ of getting used to.
Too bad for all the windows 98, windows 2000, and windows XP pre-SP2 users out there that they won't get this upgrade. Good thing they can get a better browser (today!) with Firefox ;-)