RIA Alternatives?

The maturity of RIA Services is not quite there.  So what else is there right now?  What caught my attention (in no particular order):

• ADO.NET Data Services - simple, but lots of heavy lifting required. 
• DevForce Silverlight - first impressions are very good, does have a price tag ~$1k.
• CSLA.Net - well documented and free.
• DIY async WCF solution - hmmm, doesn't sound fun.