On the whole, I dont think I can overemphasize the importance of recognizing workflow as a real thing that you, O Grand Maker of Software, need to think about as a real thing. In an upcoming article in CoDe Magazine (should be in the next issue), I talk about the importance of focusing on object-oriented design as a real thing and how it is essential to solving business problems. Workflow is another one of those foundational things that I think we need to embed in the way that we design applications, at least in the business world. The funny thing about it is that it has been there all along but only some have put the effort into thinking about it formally, just as object-oriented design has been around for a long time but few have truly understood and thought about formally.
The reason we need to embrace WinWF is that it can change the way we develop business applications for the better. The greatest strength of WinWF itself, apart from its extensibility, is that its soul is modeling, that is, visualization of both structured and semi-structured processes all the way from high-level human workflows down to basic code flow control. Taken together with strong object-oriented design, I think that we can take our applications to the next level of evolution in our industry.
In fact, I imagine a design environment where you can visually design in a multi-dimensional way the various aspects of your application. Imagine a three-dimensional representation of this as a many-sided shape, each side representing different architectural aspects of your application, such as security, network topology, logical topology, object-orientation (e.g., class libraries), business processes, services, and so forth. Each of these dimensions is a starting point to work on that aspect of the application.
Perhaps at a higher view, you could see different polygons attaching to each other via their services layer. But you interact with this in a three-dimensional way, grabbing the representation, moving it around, zooming in on a particular polygon (application), then turning the polygon around in your hand (figuratively, or maybe, eventually, literally) until you come to the dimension of the application that you want to focus on.
Choosing that dimension zooms into the next level view of that dimension. For instance, if you chose the business process element, you might see the human workflow or some business integration workflow. At each of these, you might be able to zoom in and see a model of the code flow, and at the lowest level, you would finally come to the code itself.