What is the point of hiding the Flash interface in favor of a js powered interface? This thing still relies on Flash. IT is a cool demo but completely roundabout to add an extra layer of abstraction in the form of js.
By hiding the flash core ,basically they are exposing the flash apis to javascript .This would be helpful for frontend developers who are not comfortable with flash, but want to build a decent mp3 player .Other than the advantage for developers , i dont really think there is any functional advantage for the end user.