These Whidbey screenshots definitely evoke a Pavlovian response. Previous versions of Visual Studio .NET have been some of the most pleasing to work in. Hopefully Whidbey will feel even better.
Of course the more powerful client-side apps will be the ones taking advantage of the Longhorn SDK. [Via Scott Hanselman, who has been covering the PDC extremely well, as have all the other bloggers at the PDC]