Android 4.4 KitKat rom is now available for the 3g Nexus 7 2012 aka Tilapia. The rom is pure AOSP without any modifications, with only 2 known issues:-
- Apn has to be added manually
- GPS and Auto rotate do not work
Other than that a pretty stable rom. So if you want to play with Android 4.4 KitKat on your 3g Nexus 7 2012 head over to the original thread on xda for installation instructions and download links.