Tim Anderson attended Joe's session at Mix '06 and spoke with Forest Key, Director of Developer Tools Product Management at Microsoft. His article can be found here.
On top of this, WPF/E provides UI through the vector based, designer friendly, media integrated UI XAML format. And of course the great tools in the Expression suite will edit the same project files the developers code against in Visual Studio. Taken as a package, we think this is very exciting stuff.