You can download it at http://ie.microsoft.com/testdrive/Default.html.
They are betting really hard on speed and on standards. I’ve tested it for a while and I must say that I’m impressed with it’s performance with their demos. You may also test it with some other pages but I don’t think that you’ll find something that needs that kind of speed yet, since if it was too slow developers simply didn’t do it. But I am expecting great things of it. Let us just wait that Microsoft do not disapoint us.