You can check the full release notes at:
RadControls for Silverlight Release Notes
RadControls for WPF Release Notes
The installation files are available under your accounts.
With this SP1 release we officially announce the RadDomainDataSource control.
Due to the unplanned for increase in interest in development of Silverlight line of business applications, we are making our latest addition to our Silverlight suite available before our next major release so we can enable our clients to focus on delivering their great applications without worrying about any “plumbing”. Our new Domain Data Source components ensure codeless integration of all Telerik data bound controls to WCF RIA Services. Now all the powerful data-shaping features of Telerik RadControls can directly translate to your domain service – filtering, grouping and sorting operations, for example, are performed directly on the server with minimum development effort. Our Domain Data Services support includes both a component that you can embed in your Silverlight page and a CollectionView Implementation that you can use in your view models for a truly MVVM-enabled scenario.
To explore in depth the new RadDomainDataSource please take a look at the following blog posts: