I recognize that hair shader as a BB construct and it works beautifully in P11 but in P12 it renders incorrectly. I traced back the problem to a couple of node connections but since BB constructs are usually far from simple, it is virtually impossible to unravel the connectors and figure out which one of the nodes are trouble spots. I say look for a simpler hair shader that will work in both P11 and P12.

But I do agree that until P12 reaches a point where all the problems are corrected, it's better to find some quick alternatives to keep the software afloat.