On these days, Microsoft opens it browser to public. Now u can download a beta version of IE7 directly from website and test.
Another piece of Windows Vista has been released for public.
If you're using Firefox (rulez!) or Opera you can find this refreshed browser as usual.
There are some problems, but consider this is a beta, and some old troubles on rendering css are present again.
Ok, let's link: http://www.microsoft.com/windows/ie/ie7/featuretable.mspx