Has anyone used the GP Workflow SDK?

I recently fielded a question on Experts Exchange on how to add workflow support for a Dynamics GP ISV solution.

I know that there is a Workflow SDK, but I have never installed it or looked at the documentation. I am only aware of one or two GP clients that I have worked with that used Workflow in a very limited manner, so I haven't seen the value of spending time to learn how to develop with the Workflow SDK.

The requester on Experts Exchange ultimately received a response from GP developer support with some tips on how to get started, but the gist of the response was that attempting to create a new workflow or even extend an existing one can be quite complex, and the best bet is to try and utilize an existing GP workflow.

So I'm wondering if anyone has worked on a real project that used the GP Workflow SDK. If you have, can you share your thoughts on how easy or difficult it was, and any tips or suggestions on using (or not using?) the Workflow SDK based on your experience?