This month Dev Pro Connections has an article by Milind Lele on using Sync Services in a WPF application:
With Sync Services and Visual Studio 2008 you can visually design your local data cache and have it automatically synchronize your data with the backend remote database. So instead of figuring out your own caching mechanisms on the client, you can use SQL CE to store the local data and then use the sync framework to merge data with the backend.
If you’re looking to improve scalability of your client applications then you should consider caching data that is read-only, user-specific, changes rarely, or can tolerate some staleness. ADO.NET Sync Services can really help here.
You can catch more of Milind and team over on the VS Data Team Blog: http://blogs.msdn.com/vsdata/