Result: We use our workflows to publish documents, manage large contact lists where a lot of fields are "calculated" based on certain logic, we also parse XML documents to extract metadata to add to our documents. We manage a list of employee data with picture and update Active Directory and SharePoint profile picture with our workflow. It would not be possible without HarePoint Workflow Extensions.
Bottom line: We now have about 50 workflows running on thousands of instance of list items or documents. Without HarePoint, a lot of functionality would simply not be possible.