Just posted is a nightly build of the Flex 3 SDK that will let you actually program with some of the new features in Flash Player 10. The SDK includes a new playerglobal.swc and compiler so that you can start creating Flex applications that use Flash Player 10. I haven't seen any docs yet on the new APIs but I'll try and figure out if they're coming or how you can find them. They may be out there, so if you see them, let me know. http://opensource.adobe.com