WPF/E = Silverlight
One of the reasons WPF/E is going to give Flash a real run for it's money is the video story. Unlike Flash, Silverlight (the new name) will support DRM, it supports the industry standard VC-1 codec used in HD-DVD and Blueray, and it can take advantage of the built-in media streaming capabilities of IIS. The video story is better just about any way you look at it with Silverlight as far as content providers are concerned. It's cheaper, it's faster, etc.
Add to that the fact that you get to use C# instead of actionscript as well as use XAML for your UI dev and Adobe should really be pissing their pants right now. Silverlight is so much better than Flash in just about every way. It's about time someone got it right.
http://www.microsoft.com/silverlight/