In my Biztalk projects, I had several scenarios which sounded like a great fit for HWS. I spent a fair amount of time and effort but could never get HWS to cooperate. After a while I just gave up on it and advised customers to use standard Biztalk orchestrations when possible, or leapfrog HWS and go with 3rd party Biztalk supplements such as K2.NET.
I'm happy to see that I wasn't the only one who reached that conclusion. An article by Scott Woodgate - "Choosing the right workflow implementation with BizTalk Server 2004" - makes a similar recommendation and also states that HWS has no future in it's current form and in effect is being depreciated:
"...HWS will remain fully supported with no feature enhancements in the next version of Biztalk Server. The API set will be supported by PSS for at least ten years. However, the HWS APIs will likely be removed in the Longhorn Server timeframe. In the Longhorn Server timeframe concepts from HWS will be incorporated into the next generation orchestration technology for BizTalk Server and the broader platform. It is very likely that conversion from HWS to the Longhorn Server offering will be non-trivial as no automated migration is currently planned..."