IMHO the major reason we dont see a lot more problems with DIN threaded connections is because the relatively few divers using DIN fittings are mostly either technical divers or divers that are very careful with their gear.
From my experience, DIN connections are very rugged if properly used and the threads and parts are in good shape, but it far from being a superior connection for all applications.
With a DIN connection, you are mating threads from many different manufactures, sure they are made to the same specifications, but there are still tolerances and there is a varying degree of wear, abuse, and maintenance. Also, the valve female fitting can be easily deformed (especially on the deep 7 thread DIN) if the tank is dropped or even if a technician put are wrench on the wrong place.
Personally, for the vast majority of divers, especially in rental tanks situation, I feel that a yoke connection is more forgiving
as proven by the track record of the huge rental fleets all over the Caribbean.
I would never rent a DIN tank unless the valve looked totally new. And even then I cant inspect the back side of the threads (the loaded side). Screwing my nice DIN fitting regulator into a strange tank is kind of like having unprotected sex.
