Just ran across a post on the WinFS blog that is very intriquing... if this is true then I am very excited about the future of both WinFS and ADO.NET:

"Another piece of feedback was concerns over the WinFS api’s being a different data access pattern than our existing managed code data access APIs.  Further, that our APIs were not aligned with broader data platform needs like OR mapping.  This was a big one, and as you explore the SDK and the APIs, you will see the beginnings of how we will be addressing this.  We are in the process of building-out the next version of ADO.NET to have new features that provide a data model, object-relational mapping, and flexible query infrastructure.  The new data model is about entities, and the WinFS data model of Item types is built on that model.  Looking through our SDK and code samples you will see how Items are composed of underlying entities.  OR mapping is a big requirement - WinFS is a very prescribed mapping (defining a type in WinFS generates both the underlying storage schema and the partial class to program to that type)."

If they solve the OR Mapping problem for us, and we have a single API that works for both SQL Server and WinFS, that would be huge.