A few folks have asked about using the Silverlight Beta 2 client library against a data service created using the recently released .NET Framework 3.5 SP1 RTM bits. In general, the Silverlight Beta 2 data services library was created to target the .NET Framework 3.5 SP1 Beta release of ADO.NET Data Services server side components. While the Silverlight Beta 2 data services library may work in some scenarios against a .NET Framework 3.5 SP1 RTM server, you should NOT count on the two being fully compatible with each other.
Now that we rev'd the server side with this release of .NET 3.5 SP1 RTM our current task is to update the Silverlight data services client to work well with the RTM'd service side. In the Silverlight RTW timeframe the data services Silverlight client will be updated to be fully compatible with the .NET 3.5 SP1 RTM server side components.
In future, this type of impact will be minimized because as part of our last few .NET 3.5 SP1 development milestones we added a versioning scheme directly into the data services product to make client and server rev’s tolerant of each other where possible.
Program Manager, ADO.NET Data Services