Your not alone, and no - nothing in that Apple technote is useful. At all.
On my Kenwood stereo, it has an aux in that if I plug into my headphone jack on the iPhone I at least get audio - what's annoying is the stereo can still control my iPhone through the USB/Dock connection - I also get song titles, album art, etc. Audio just stopped being carried over USB.
And NO, it is NOT a problem with my stereo. The only thing that changed was iOS on my iPhone. I didn't do the software update on my stereo, so why many people in other threads are trying to push it off on the accessory makers is beyond me. My Kennwood stereo is a LICENSED Made for iPhone accessory - iOS7 broke it's functionality, NOT the other way around
I had the same issue and resolved it by doing the following.
- Remove all Bluetooth pairings from your iPhone in Settings > Bluetooth. Be sure it's on and tap the ⓘ next to each device. Tap "Forget this Device".
- If you are able to remove them from your accessories (including cars) through some similar process, do that as well.
- Close all apps on your iPhone by double-tapping the Home button and swiping up on all apps to flick them off the screen.
- Power-cycle your iPhone by simultaneously pressing and holding the Home and Sleep/Wake buttons until you see the Apple Logo. This can take up to 15 seconds so be patient and don't release the buttons until the logo appears.
- Once the iPhone restarts, pair it with the car again.
- Try it. If it works, great! If not...
- Note you may have to do this more than once. Mine took three tries but eventually worked.