JWR66V or JSS15J, what's up with that?

We're getting a lot of requests and people overall seem to be confused by Googles move to release two branches with the same build number.

Trying to make this easy, read if you intent to change your kernel or build roms.

JWR66V is Googles official release branch, this is what the Nexus 4 runs stock. This branch is tested and stable.

JSS15J is an experimental developer branch that officially only runs on the 2013 Nexus 7. This branch is not stable any other device and suffers from severe issues that affect all JSS roms (and as it turns out even the stock Nexus 7. http://goo.gl/dWIO0g)

These issues weren't clear to developers in the beginning, most teams assumed newer = better and built JSS. XDA was consequently hammered with complaints and bug-reports,mostly dead-locks/freezes.

Now some teams have accepted these issues and wait for Google to fix it. We did not accept it and reverted parts back to JWR while retaining obvious JSS bugfixes, we still cherry-pick aosp/master bugfixes as welll. This is not a downgrade, many users have reported 4.3 runs now stable for them.