It's not all about the music. For example I find that inputting a destination using the voice commands is slow, unreliable, and a generally frustrating process. On the other hand, Siri gets addresses right about 90% of the time and I don't have to waste breath confirming every piece of info I say. With the new turn by turn navigation integrated into ios6 ill probably use that for navigation. Plus there's a bunch of other use-cases for air play that are not available to me through the aux jack.