I had just done a clean flash of 4.2.1 earlier today for some testing, unrooted (but unlocked of course). I copied the update file to the internal storage in Windows, rebooted the N7 to fastboot mode, then I used mskip's Google Nexus 7 Toolkit to boot from recovery temporarily since it wasn't installed. Installed the 4.2.2 update like any other flashed file and rebooted, now running 4.2.2 without issues (I did a factory reset after it was installed just in case).
Haven't noticed anything different so far, hoping to see a release notes or change log soon so I can figure out what this rather large update seems to have accomplished.
So far so good I suppose, going to remain "pure stock" for today, maybe tomorrow. Making a backup of this just in case as well to save issues and time with restoring it for obvious reasons.