Thanks for contacting us and for your inquiry.
In general, all of our controls have Visual Studio and Expression Blend design time support. We have performed tests here and have not noticed any problems. However, we would like to receive some further details (screenshots, steps to reproduce and stack trace info) on the issues that you experience so that we can make sure that the controls work as expected in the mentioned environments.
Thanks for your understanding and do not hesitate to get back to us in case of further questions.
the Telerik team
Let us know about your Windows Phone 7 application built with RadControls and we will help you promote it. Learn more>>