The most notable addition is something called "Bluetooth Sharing." Apple's change log for iOS 6 developers doesn't say what the feature will be used for, but we have some good guesses.
First, Bluetooth sharing may make it easy for you to swap photos, videos, links, and other media with nearby iPhones. Samsung has a similar feature in its Galaxy S III phone, but it's a pain to set up and use.
It's also possible Apple will want to incorporate Bluetooth Sharing with its new Passbook app. Passbook acts as a virtual wallet for your gift cards, concert tickets, boarding passes, etc. It's feasible Bluetooth Sharing could be used to make payments from Passbook. (Although this seems less likely as not many merchants accept payments from Bluetooth devices.)