There is definately a battery drain issue with KitKat.
Vanilla N7 2012 - all default settings (no apps) with wi-fi off and no sim. From 100% battery took 4 days (exactly 96 hours) to go to 17%.
Allowed update to install Kitkat. Again, all default settings (no apps) with wi-fi off and no sim. From 100% battery to 0% in 11 hours (may have been less - had a lay in, it was Sunday
).
Reset tablet back to vanilla/factory and repeated (default, no wifi no sim); 100% -> 18% in 96 hours.
Looking at the Battery info; 'Android Idle' is the culprit. Not sure if this is a general catch-all (IE. Other processes are reported within 'Android Idle') or not - being a bit of an Android N7-noob - but the tests above kinda indicate KitKat - or something within the OS update - is a bit power-thirsty in Idle mode....