We did not include direct web service support in DevForce 2010, for either publishing a web service as you were doing, or for consuming a web service.
In DevForce Classic, entities and entity graphs were not directly usable from a web service without a bit of help in marking them up for serialization, and in providing a base WebService class with helper methods. In DevForce 2010 the entities and graphs are easily serialized, so there's no need to provide these features. You shouldn't have any problems in creating a web service backed by DevForce entities on your own, but if you have additional questions or problems let us know.