Don't get me wrong it is a great service and if it was in the wifes vehicle you bet I would have it. But I know how to take care of myself if the vehicle breaks down. Plus I have a cell phone and I'm never more than 15 miles away from the next town.
I like it for it being able to connect when even a cell phone could not, like when I am headed up to Yellowstone.
Been on some state HWY that you could drive for an hour without seeing anyone.
Hit a deer, bison, bear or anything like that some dark night or get whacked by a drunk and not be able to call anyone you do have a chance if onstar detects the crash.
From what I have read Onstar has more then just the air bag detectors on the newer cars.
Service is "okay". A few occasions when I had to request driving directions during rush hour, I had to wait on average about 3 to 5 min. for help. After the free trial, I realized that I just don't use it regularly. If you have AAA, a cellphone, keep up with maintenance and don't go off path, you'll bore the operators. I do use it when driving long distance and just pay for that month.