I'm just taking my first look at the RadDock control. The "Getting Started" instruction seems very straightforward, advising me to add a reference to Telerik.Windows.Controls.Docking to the project and then select the RadDock control from Blend's Assets.
The documentation is here: http://www.telerik.com/help/silverlight/raddocking-getting-started2.html
The first alarm bell is the icon shown on the screenshot is different from that you get (which is a push-pin button not the angled bracket icon shown in the documentation - screenshot attached)
When you click the icon it just sits in the toolbar greyed out. You have to go back in and select it again and then it changes to a selectable state, but simply double-clicking on the RadDock control does nothing other than crash the designer with "An Exception was thrown: ArgumentException: Property Width not found in the property collection".
I have tried this on one PC running Windows XP, Blend 4 and 2010 SP3 SP1 and on another PC running Windows 7, Blend 4 and 2010 SP3 (without the SP1). The problem is easily reproducible and gives me no confidence in the control at all - I haven't even started doing anything with it yet just tried to add it to an empty user control.
What am I missing?