I like to think I have a good working relationship with Telerik, they are probably the best component vendor I've worked with at any level. They listen to the needs of their customers and do the best they can to help out.
Their controls get used in 99% of the ASP.NET sites I build.
As a dot net developer its good to her something good about third party vender. That will give me some confidence in telekrit when going for 3rd party tool
I have used Telerik for the last couple of years and their support is excellent. Whenever we had a problem they were quick to respond with a fix or workaround. I also found there support staff very friendly and helpful.
+1 for everything good said about telerik. They've been terrific supporters of the .NET community (user groups, code camps, etc.) in addition to being top-notch folks with a great handle on how to take care of customers.