Some very interesting stuff here.
UPDATE: Just reading that article, things I'm looking forward to most are the URLMapping (Rewrite.NET is cool and all but it will be nice to have the new 'native' model) and 'No Compile' - I have been waiting for this for SO LONG, JSP has had it pretty much since day one, that ASP.NET has not until now had this feature was a major omission - finally, we can protect ALL the source for our apps!
Incidentally, after the PDC I'll post some more stuff here about some of the new stuff in Whidbey - there are some very cool additions / changes which Scott has not yet mentioned ;-)