Joe Stegman, lead program manager on the WinForms team (.NET client) has one of the more impressive demos we've seen.
Check this out. You can build a clone of Outlook in 100 lines of code (using the next version of Visual Studio and Windows Forms).
For the significance of this we need to take you back to the early 1990s back before we first saw Visual Basic. It used to take 400 lines of C code just to draw a Window on the screen back then.
The Windows Forms website has more demos and samples. Don't miss the first part of Joe's demo where he shows off other Windows Forms-based applications including an app that looks very close to MSN Messenger but is actually built completely in .NET.