All the fear, uncertainty, and doubt around here. I've already posted in various other threads about this, but if you buy either of the Lightning adapters, everything will work EXCEPT video playback and iPod Out, aka PlugIn, which is the native iPod video interface that you can put up on iDrive. But both of those features require that you have BMW Apps and the Media cradle. Obviously the 5 won't fit in the 4/4S Media cradle, but people were thinking that if you buy the extension cord-style Lightning adapter, you'd be able to attach the 5 to the dock connector in the Media cradle and get it. Well, you won't. But as others have said, that function is pretty useless anyway. If it's important to you, wait for the 5 Media cradle -- you'll likely be waiting a while given that the 4 cradle took about 7 months to be released (then immediately recalled and not reissued again for 3 more months), and the 5 cradle will likely be more expensive since it will have to include a video DAC because the iPhone 5 only outputs digital video and iDrive only accepts analog.
Everything else, including Bluetooth calls, Bluetooth audio (with Combox), and the regular USB music connectivity will work just FINE, people. Settle down.
And for the micro-USB lovers out there, yes it might be more convenient, but the dock connector was able to support a whole lot more than would have been enabled by micro-USB, including analog video out (composite, S-video, and component), HDMI out, amped analog audio, and line-level analog audio to name a few. I'm sure that tradition will carry on with Lightning as Apple develops future products. Could they have included a microUSB connector as an alternative? Sure, but anyone who knows Apple knows that they don't implement things with functional overlaps. Not saying that that makes micro-USB automatically worse, but it's not as if Apple decided to just reshape a micro-USB port without adding any functions purely to be proprietary.