There's no lack of blog entries about this.... but I'm going to add my two cents worth. Scott Guthrie spent about an hour demonstrating the new ASP.NET MVC project that should be released to the public.
This is one of the coolest technologies I've seen in a long time. The MVC project team designed based on a few very important principles -- separation of concerns, extensibility, and designed for testing.
Let me say this again.... Microsoft is working on a development tool that is designed for testability out of the box.
From the prototype that Scott demonstrated, Microsoft has this one right.
One of the other exciting features that stayed a little bit under the radar is this -- the MVC framework is intended to allow the developer to plug in whatever IOC and/or dependency injection package they want. Microsoft has (at least at this point) decided to allow the developer to use whatever tool they like, rather than having a prescriptive out-of-the-box solution to replace those solutions that already exist in the user community.
Look for the first beta drop in 6-8 weeks.