Excellent Screencast. I used WF in 2008 / 3.5 to back WCF services and ended up with a rather ugly learning curve to get some of the bits talking and working correctly. I would have loved to have had a screencast like this one then...
Really excited about the updates to WF in .Net 4 as well... looks like the tool is maturing nicely and is going to be a very powerful addition to the developers toolkit. This is especially true when working with complex business processes that need some level of human interaction. The thought that business process design and updates can be communicated in a domain specific manner and even possibly delegated away from the development teams to the actual subject matter specialists is, quite simply, awesome!
Keep up the great work,