While I was working on a SilverLight 4 demo I found out that Entity Framework is not supported directly through the .NET provider or ODP tools. In order to make them work you need to either write a wrapper of your own (wouldn't chance it) or else use a provider like DataDirect or Quest's upcoming tool. So far, I've been very happy with the DataDirect tool (found here http://www.datadirect.com/products/net/index.ssp). As I get a little farther along I'll post more on SL4, RIA, and EF.