Twitter #Music got its big public debut today, and at first blush the service is visually impressive, well-designed and features smart, opportunistic integrations. Those integrations, with Rdio and Spotify, completely change how the app works for users who have active accounts with either service, vs. those who don’t. And the biggest winners here might just be Rdio and Spotify, since the app experience reinforces just how strong they and other discovery services like Songza really are.