The only offficial announcement was in mid-August and did not say much. There have been a lot of posts but no real information.
Until there is either an offical revelation or a TSB (and am surprised there hasn't been one), we are just guessing.
That said what we know is that:
1) Usually affect #2 and sometimes #4 cyl
2) Is characterized by misfires in #2 and #4 cyl (most scan tool programs can display, is part of test #06). Codes P0300, P0302, and/or P0304 may be set
3) Valve guide damage has been mentioned - would explain need to replace head.
4) Manufacturing error has been mentioned but would not explain 3-4 different part numbers for driver's side head
5) Comments in posts could be consistant with hot/lean detonation. However it was said that heat was not a factor
6) "Betts said the problem has been found in about half of 1 percent, or about 7,500 of the about 1.5 million Pentastar engines" - Autoweek.
7) Most have been in Wranglers though other instances (WK2) have been seen. All of the car lines mentioned are large, heavy vehicles.
Bottom line: CJF has not said anything since August though with a return of cool weather the incidence seems to have dropped off.
We need either someone who would understand to examine both a failed and a new head or for CJF to issue a TSB.
ps found a reference that a valve seat was found to be "oblonged". This would be consistant with a valve guide problem and cause a leakdown test to be low.
See also Update on ticking Pentastar..new head... - Page 116 - Jeep Wrangler Forum