If you've recently updated your Nexus device from Jelly Bean to KitKat, there's a chance you're already being notified of an OTA update to KRT16S. If you're wondering what's changed, the collected list of source commits has been posted by Al Sutton. Most of the tweaks are pretty minor, including an improvement to the backup service, a few updated APNs for assorted carriers, and code to handle rare issues with the 3G Nexus 7 (2012) radio.
Back on Halloween, Google promised that proprietary binaries and factory images for the Nexus 4, Nexus 7, and Nexus 10 would arrive shortly after devices received their OTA updates. Even though some OTAs haven't even rolled out yet, as of a few minutes ago, all modern Nexus devices now have Android 4.4 KRT16O factory images and drivers available for download.
This means you can flash stock Android 4.4 onto any supported device, even if an OTA either wasn't available yet or wouldn't work for some reason.
Following closely behind the 2012 and 2013 Nexus 7 KitKat OTA updates, it's finally the Nexus 10's turn to receive the same treatment. You can now flash the 219MB KRT16O Android 4.4 build without having to wait for your tablet to alert you, no matter what your rooting/bootloader situation is. Of course, if you've modified the system partition in such a way that the OTA won't apply cleanly anymore, you have to either revert those changes or wait for the factory image.
Yesterday, Google announced the kickoff of the KitKat OTAs for the Nexus 7 and 10, though we haven't seen the update for the 2012 N7 actually pop up until a few minutes ago. (If you have a 2013 Nexus 7, head over here.)
2012 Nexus 7 Wi-Fi (not 3G yet) owners, listen up. You can now flash the 185MB KRT16O Android 4.4 build without waiting any longer, no matter what your rooting/bootloader situation is.
Last night, roughly two weeks after the Nexus 5's release, Google announced the first round of KitKat updates for the Nexus 10 and 2012/2013 Nexus 7. While most of us are still waiting our turn, maniacally mashing the Check for updates button, the over-the-air update url has been discovered.
That means you can easily flash the 243MB KRT16O Android 4.4 build right now without waiting any further, no matter what your rooting/bootloader situation is.