This seems to be a recurring theme with Apple iPhone updates. The updates seem to change some of the code that controls Bluetooth functions. Without updates to your hardward (in my case, JVC and Panasonic car audio decks), the update renders some of the functionality useless, in particular the audio controls for music.
The 'fix' is to use a now 'broken' piece of hardware until the manufacturer makes available a firmware update for the audio unit, have it removed from the vehicle, take it in to a service center and have the firmward installed, then pay for a re-instal. Well, maybe you can do it on your own, but the updates are not available for a while, if ever, so....
All I know is that the exact same thing happened to me with the previous update and I'll NEVER update my iPhone again for that reason. Major hassle. I'd rather have the old OS and a functional phone/car audio/bluetooth system in my car.
It would be nice if there was some backward compatibility built into these updates from Apple, but they seem to rule the roost. Incidentally, if you download the new version of IOS, apparently you cannot un-install it to get back to normal.