Okidoki, I have been experimenting the last hour with iOS 6 on an iPhone 5.
Initially, it synced in bluetooth okay, but then wouldn't connect again. I restarted the phone, un-paired, and re-did the pairing. And it went fine after that.
There's another thread elsewhere that we've been running about the set-up for the Messages features (text-message only, usually). It really gets going at post #82, so you can save time by skipping to that and carrying on.
As for using the iPhone 5 Lighting cable-to-USB (center-armrest of BMW):
I just used the the cable that came in the box with the iPhone 5, and it does everything that the iPhone 4s did. Calendar, Facebook, News feeds.
It did not (as expected) do a software-based "Plug-In" connection [the snap-in Media Adapter.]