Windows Workflow - A Paradigm Shift
I think much of the resistance Microsoft is going to face in the WF space is going to come from the paradigm shift we're required to make, especially in the whole framework vs. server space. Most people who have used workflow tools, such as K2.net and Biztalk, see them purely from the point of view of business process workflows and also with an understanding only of sequential workflows.
The sequential vs. state machine issue is less of a direct issue, but in some ways it's part of the same discussion because it's about the mindset. The people I'm talking about need to break the mental / marketing barrier to see how WF can have great power for other purposes as well, like UI flow, dynamic line of business applications (through designer re-hosting) and the ability to use to create any kind of dynamic, flexible flow or state-based "algorithm", so to speak. The idea of workflows also not only being hosted within a server but really just graphically modelling code, even on the client machine, is also going to take some getting used to....
It's going to be a very interesting space and the onus is on us who're passionate about knowledge sharing and community to make sure we get the right message out because I believe this product deserves some serious attention.