Apple has introduced a slew of changes in the General screen. For starters, it no longer contains the Bluetooth option (which, as noted above, has been moved to its own item in the main Settings list). On the iPad, iOS 6 removes the Network item and moves the VPN section up one level--the other items under Network in iOS 5 (Wi-Fi and Personal Hotspot) have their own top-level entries.
On the iPhone, the Network item has been renamed Cellular, and new here is a group of settings that let you choose which features (iCloud Documents, iTunes, FaceTime, Passbook Updates, and Reading List) can use cellular data. Note that to allow FaceTime to use cellular data, you must have an eligible cellular plan--AT&T, for example, requires that you subscribe to one of the company's Mobile Share plans in order to use this feature.
On iPads, the Usage screen now includes information on usage and standby time since the last full charge (options that were previously available only on the iPhone).
The Auto-Lock screen has gained a Never setting on all devices, and a 15-minute setting on the iPad. On the iPhone, the Require Passcode option in the Passcode Lock screen has gained settings for 15 minutes, 1 hour, and 4 hours. (Interestingly on an iPad 2, this screen actually loses a few options.) On iPhones, there are also new options to allow Passbook access when the device is locked, and to allow you to use iOS 6's new Reply With Message feature (see Phone, below) when the phone is locked.
The Restrictions screen no longer includes an option to allow YouTube, since iOS 6 no longer includes the YouTube app. However, it gains such an option for the iBookstore, and there's also a new Books option under Allowed content that lets you choose whether or not to allow books with explicit sexual content. The Allow Changes options now include one for locking the phone's volume limit (previously located in Settings -> Music -> Volume Limit), and the Location item has been moved into a new Privacy section that mirrors the options in the new top-level Privacy settings; for each type of data, you can choose whether or not to allow changes, as well as decide which apps have access to that data. (You can change many of these settings in the top-level Privacy, Twitter, and Facebook screens, though you can't access those screens if restrictions on them are enabled.)