For those still having issues with pairing their Bluetooth to their car or any other device, maybe my experience can help. I went from an iPhone 4 to an iPhone 5 about 3 weeks ago. My iPhone 4 worked perfectly with my car ('07 Acura TL) and my Jabra Bluetooth headset. As soon as I switched over to iPhone 5, I couldn't connect to Bluetooth at all. I also had a few apps that kept crashing. I tried everything outlined in this forum and 2 other forums, and it still wouldn't connect. I called Apple and they told me I would have to contact my car dealer to get my HandsFreeLink system updated. That didn't sound right to me, nor did it sound acceptable b/c I knew people with older cars who could connect their iPhone 5, and I also knew not everyone with the 5 and/or iOS 6 had these issues.
I made an appointment with the Genius Bar at my closest Apple Store yesterday. It turns out my issue wasn't my car, it wasn't my Bluetooth headset or the iOS itself. For some reason, when I backed up my iPhone 4 via iCloud, something in that backup corrupted my iPhone 5. After running a diagnostic on my phone, the rep from Apple explained to me he'd have to completely wipe my phone (this is different from a Reset, which you can do from your handset). I had my Contacts saved on iCloud but other than that, I didn't bring anything else over from the iPhone 4 once the iPhone 5 was wiped out. In other words, if your issue happens to be a corrupted backup, you can't restore from iCloud once the iPhone 5 is wiped. So once everything was removed from my iPhone 5, I transferred my contacts over, then had to manually add back the apps I wanted. I also lost all my pics that were not in the Photo Stream, but that was no big deal for me since most of mine were saved to a computer. Once that was done, I was able to connect to 3 different bluetooth devices with no issue, including my car.
It's a relief to finally have this resolved after 3 weeks of inconvenience whenever my phone rang in my car, trying to use my iPhone headset to talk. I know it's a pain to have to set your phone up all over again but I'm glad to just have it WORK!