Have you tried out the Web Client Software Factory from Microsoft Patterns and Practices? It's up on Codeplex here. There have been some reported issues with opening the Workflow model in design mode in Visual Studio as outlined on this thread. If you have seen those issues, please vote for it on our WF Connect site. And if you have additional information or a good work around you've found please also list that on Connect.

Here's the direct link to the issue on the WF Connect site. You will need a passport login to get to it.