The meat is the Player class and the IPlayer interface which wraps the YouTube proxy object. The Player extends UIComponent and implements IVisualElement so it works decent with Flex 4. The original SWFProxy object extends Sprite which is fine for Flash but not for Flex.
If you are to lazy to study the API docs like me this screenshot might help:
The example is still pretty small but I’ll try to extend it when I find some time in the future.