We strive to improve our controls in every release that we produce.You should use whenever possible the latest release because that guarantees that much of the previous issues are resolved while the functionality is preserved or developed. Having issues with some of the new releases, should not make you look back in the past for previous releases. That is why we provide support to our customers. We are always on a lookout to hear from our clients, what are the problems they experience, what new features they want, what should be changed in the next release and everything that could improve our products and customer's experience.
If you have some particular problem with the 2011.1.519.35 release, please open a support ticket and let us know what is the problem. We will be glad to help you achieving your goal.
You could find specific information on what was changed through the different releases here:
the Telerik team
Register for the Q2 2011 What's New Webinar Week. Mark your calendar for the week starting July 18th and book your seat for a walk through of all the exciting stuff we will ship with the new release!