A workflow model consists of reusable "blocks" known as activities. We construct our workflows by assembling activities into a flow.
WF enables us to embed the workflow within our solutions, exposing workflow capabilities directly to our end users.
WF's extensibility coupled with its ability to be embedded within our solutions enable us to use workflow in ways we may not have previously considered.
So how are you using workflow?
If you are at TechEd make sure you stop by the WF booth and pick up some swag. These little babies are going to be collector's items one day.