Finally, hidden in General > About > Advertising is a new setting called Limit Ad Tracking. If you tap Learn More, at the bottom of this screen, you see Apple's own explanation of this feature: "iOS 6 introduces the Advertising Identifier, a non-permanent, non-personal, device identifier, that apps will use to give you more control over advertisers' ability to use tracking methods." If you enable the Limit Ad Tracking feature, apps cannot use this Ad ID to serve you targeted ads.

On iPhones, the iCloud settings screen now includes an option for syncing your Passbook data, and on all devices, the Photo Stream item now includes a toggle for Shared Photo Streams; if the latter is enabled, you can create photo streams to share with other people and you can subscribe to other people's shared streams.

The biggest--and most welcome--change in the Mail, Contacts, Calendars screen is found when you tap Signature. Instead of a single text field for a signature that appears in all your messages, you can choose between All Accounts (which gives you that single field) or Per Account. The latter setting offers a separate signature field for each email account you've set up on your device. Type or paste your preferred signatures, and Mail will automatically append, to each outgoing email message, the appropriate signature for the sending account.

Also new here is an option to be notified about changes to shared calendars. On the other hand, the Mail, Contacts, Calendars screen loses the setting for minimum font size in Mail, as well as the section for Reminders settings; the latter has been moved to a new top-level Reminders item.

The big change here is Reply With Message. This new feature lets you respond to incoming phone calls by sending, with a couple simple taps, a text message to the caller. The Reply With Message screen lets you configure up to three stock responses, such as "Can't talk right now...I'll call you back in a bit."