Just as we saw this morning with the Nexus 4 and Nexus 10, the Nexus 7 is getting updated to Android 4.2.1 via an OTA update. There's nothing groundbreaking here, its simply a bug fix for the omission of December from the people application and an update to add joysticks and gamepads as HID devices.
But updates are updates, and we know that plenty need to get them ASAP. Thanks to XDA, the manual download link is available and advanced users can flash at will. You'll end up with build number JOP40D, and everyone you know that was born in December is now allowed to get a year older again. Grab the OTA package below, and head into the forums for questions about flashing.