RadControls for Silverlight are compatible with all browsers, supported by Silverlight. There is some additional functionality, that depends on the browser, such as the Mouse Wheel support and Right Mouse Button support, which is browser dependent. These features need the Silverlight plug-in to be in windowless mode, which is not supported by Safari on Mac. The browser dependent functionality is not UI, so you should get the same visual result in all browsers.
If you send us a simple sample application that demonstrates what's wrong with your project, we can provide some guidance.
the Telerik team