I am badly waiting for RIA support on 4.1 model-first (LinqToEntitiesDomainContext<TContext> where TContext : DbContext - is's not supported yet).
Also, you shouldn't have to decorate your POCOs with the nasty Key attributes, the goal is to have generated POCOs that RIA processes and decorates automatically for the client (perhaps via DomainDescriptionProvider).
Anther thing I couldn't come along is how to share interface implementations over the wire, please vote for it.
My wet dream is model-first only, and this should generate database (should have more options), server entities, auto-decorated client DTOs that implement interfaces generated from POCOs (undecorated at all) + full MVVM support (i.e. relaxed while very extesible data manipulation controls for the VMs that can be (or not) exposed to the Views)