Google is yet to officially acknowledge Android 4.2.2, but we can confirm that the over-the-air update has started rolling out to Nexus devices. It's a minor upgrade with little in the way of user-facing changes; Android Central has rounded up the more notable enhancements, including fixes for rebooting problems and Bluetooth audio issues.
The biggest user interface change we've noticed is a tweak to the quick settings introduced to the notification bar in Android 4.2: whereas before tapping Wi-Fi or Bluetooth would take you to the relevant settings screen, you can now switch them on or off directly with a long press. That's a speed improvement, but an inconsistent one — the neigboring airplane mode, for example, is toggled with a quick tap.
Notifications for app downloads have been made more useful, too, as you'll now see a progress indicator that includes the remaining time. We're also seeing much faster image loading in the Gallery app.
Overall there's little to get excited about in Android 4.2.2, but the changes behind the scenes may turn out to be the most important. Anecdotally, Android 4.2 has always seemed slightly less stable than 4.1, so a bug fix update could be just what's needed. If your device hasn't notified you of the update yet and you're comfortable with manual installations, Android Central has provided direct download links for the Nexus 4, Nexus 7, Nexus 10, and GSM Galaxy Nexus.
Update: As pointed out in our comments and by Brian Klug of AnandTech, the 4.2.2 update blocks the unofficial workaround that enabled LTE connectivity for the Nexus 4 on certain carriers. This doesn't come as a surprise, but anyone using that tweak