I'm curious to see the full list of which features are only available to people who own newer devices (ala Siri only on the 4S last year). The big one for me is that for the new Maps app, turn-by-turn directions and Flyover will only be available to those who own a 4S or newer device. I don't have plans to upgrade my device this year (yet) and while I'm pretty sure the iPhone 4 can run turn-by-turn--there are in fact already a number of App Store apps that offer it--it's fairly typical of Apple to deny older devices some of the best new features, whether or not the hardware differences justify it.
So: what else are older devices not going to be getting when iOS 6 drops?
So: what else are older devices not going to be getting when iOS 6 drops?