It's faster processors, but the big win (if you can call it that) is advanced voice recognition which costs $20 a month. You can dictate emails and such, but it's really a revenue stream to bring pricey apps to us. I'm sure it'll work with current iDrive systems too.
I'm more excited about Apple's "Eyes Free" BMW integration with iPhone 5 and iOS6 which will do the same thing for iPhone users. This was mentioned at the June keynote by Scott Forestall and BMW shown as a launch partner by May 2013.