I am currently using Telerik.Web.UI Version 2011.2.906.35 -- I just grabbed it off the latest internal builds.
radNotification = $find(radNotificationID);
"Dashboard saved successfully."
This is what I was using to try and set the appropriate fields. I am able to see the title set to "Test", but I do not see the text set. Yet, the alert DOES display "Dashboard saved successfully." so I believe that the property has been set successfully and is just not being rendered?