This is a really powerful tool, nice job on the demo Corey, much appreciated. It was mentioned that most developers are still using the Visual Studio to edit XAML, and I don't see that changing unless Blend comes out with an express (aka Free) version. In the era of free development tools Blend is probably never going to become mainstream, or the "default" when editing XAML.
Most developers are not going to buy the MSDN premium including myself. I am an action pack subscriber, however, I think it offers a lot for the money but not Blend.