We have OnStar on one of our cars (and the prior one). My wife rolled her last car 3 1/2 times and ended upside down in the street. The air bags didn't deploy so no OnStar. It seems to me if your car is upside down, it should call somebody.

So with that in mind, we've ever have even used it. If I remember though you give them your name and address and then the PIN. Which brings up another problem... "uuuuh... I can't remember my PIN".