Hi GEB,
We will release RadControls for Silverlight, built against the Silverlight 3 assemblies, a couple of days after Silverlight 3 becomes official. It will include the official RadScheduler for Silverlight that will be released for Silverlight 2 with Q2 2009, in the beginning of July. However, a build that will contain all features of Silverlight 3, such as validation, etc., will be released with SP1, most probably a month after the Silverlight 3 release.
Best wishes,
Valeri Hristov
the Telerik team