A while ago Shawn Wildermuth wrote a post about the state of data access in Silverlight and now he decided to update it with some new information.
The three options for data access are still the same "Web Services, WCF Data Services and WCF RIA Services". My major issue with data access today in Silverlight persists: there is no perfect answer. There is give and take with each approach and giving good advice about the right one is difficult.