Actually Josh, I was going to start another thread regarding the iOS 6 version.
I've been beta testing iOS 6 for a little while, and since the latest version was released many connectivity quirks that I used to have are now completely fixed.
I am using iPhone 4S with iOS 6.
The main issue I used to have (that is now fixed) is that if the phone was already connected with bluetooth, and I connected the USB cable, switching from the Bluetooth tab on the CX-5's screen, to the iPod tab would result in silence. This would be rectified by changing the audio output manually on the iPhone.
iOS 6 fixes this. It can now be connected with Bluetooth, and connecting the USB cable causes the phone to automatically steam the audio correctly.
No manual change required now.
Further to this, it seems Bluetooth performance is a little better.
It was bluetooth performance that was the cause for using the USB cable in the first place. 30 minutes on bluetooth, and the audio would start to stutter (as if it was having issues buffering). The USB connection would be fine possibly due to not requiring a buffering of the audio.