ASP.NET AJAX 4 adds to client-side data scenarios for both page and component developers. JSON data from the server can be rendered as HTML UI on the client in a highly manageable and efficient way, using ASP.NET AJAX templates.
A key aspect is support for ADO.NET Data Services.
You can try out. The bits, reference, samples, and source code are available on CodePlex at ASP.NET AJAX 4 Preview 4.