We have it on both of our vehicles and have had for several years. In about 2002 they went from analog to digital as almost all towers changed then and their coverage was reduced some what.
We have had life saving experiences with OnStar. While we were on vacation with our son and his family out side of Durango,Co. They had a medical emergency and headed to the hospital in Durango in the middle of the night. They got lost on a mountain road in the dark and called OnStar who told them to park and they would dispatch an ambulance and paramedics to them which they did and were able to get our daughter-in-law into surgery just in time to save her life. Another time I was driving to visit my granddaughter and had a stroke in route. I was able to push the button and Medics were dispatched in time to help me so I was lucky enough to not have any long term effects from the stroke.
It is expensive but we feel worth every penny.
ArizAl