I'm trying hard to keep myself out of this conversation, but I do want to add that:
1) There have been very few document occurrences where people claim the car was all stock and the DS broke
2) Within those occurrences, nearly every single one of those cars had been driven hard prior to the occurrence
3) Assuming only 10,000 mustangs were built (yeah right, lol) and 50 of them were reported with a DS failure (I've yet to find even 15 report a broken DS), that's still less than half a percent. I believe in those instances something else was afoot. Like a QA inspection.
I've exceeded 115MPH on various occassions, have had my car dyno'd numerous times, have aftermarket gears and my DS is still holding strong.
Past: 2011 3.7 6AT SG
Current: 2014 5.0 6MT Black