Other than valve failures, what other problems has the 6.7 had? I understand it's being "freshened up" for the 2015 model year, but I would hope it's still an improvement over the 6.4 disaster. I can say one thing, after seeing one disassembled at the Truck Nationals at Carlisle last summer, "it aint no Cummins".
Regarding ownership by Fiat, look at the alternative- Bob "Home Depot" Nardelli. He would be doing exactly what he did at HD- sell the cheapest crap possible regardless of the "cost". No wonder they gave him $210 million to go away.