You can work with ADO.NET DataSet objects to retrieve and submit data in InfoPath SP1. Note, however, that there are limitations when working with a DataSet. I have a technical article on MSDN that illustrates how to design a form based on a DataSet while also discussing some of the limitations.
In the next week or so, I will also have a technical article regarding integration between InfoPath and Human Workflow Services (HWS). I will post again once that article is made available on MSDN.