Yeah, I blew mine up a week ago... chewed a 5 teeth off the pinion gear. Good thing it happened on the way to the 4wding not actually out in the bush.
I have just picked up the center rebuilt with an ARB air locker and hardened crown and pinion. From all reports it should be pretty tough.
As the other guys mentioned, these diffs are pretty strong and would take a blown motor to tear the gears... that being said, wear and tear or driver abuse is the main cause of pinion/crown failure.
In my case... old age (1985 model) of the diff, previous owner had a Chev V6 doing all sorts of heavy towing and heavy loads, so wear and tear. The bearing lands also showed signs of flaking, so the old fella had enough on a number of different fronts!
Cheers,
Shuey