Currently our installers will only allow you to have different major versions installed side by side. For example, you can have Rad Controls for WPF Q2 2009 and Rad Controls for WPF Q3 2009 installed on the same machine. The scheme is bit different when you are dealing with releases from the same Q - for example, Rad Controls for WPF Q3 2009 SP1 and Rad Controls for WPF Q3 2009 SP2 cannot be installed side by side. The latest Q3 version will always remove the previous Q3 version.
There should be no problem installing different versions of our WPF controls on one machi - every Q is installed in a different folder and controls from different Qs are added to different tabs in Visual Studio.
the Telerik team