Shawn Wildermuth has published part 1 of his article on using RIA Services, MEF and MVVM with Silverlight 4.
Recently I blogged about Brad Abrams' PDC RIA Services Talk and complained about the data source functionality. While the drag-n-drop ability in RIA Services is interesting, I believe that it may be a bad approach for all but the smallest of projects (or one-off projects). In that comments of that article, I promised to show you how I would architect a Silverlight solution with RIA Services.