We have OnStar on two vehicles and use it frequently. However, we had an issue last fall in northern Georgia mountains. We needed directions and kept getting interrupted before it could download. Then, we couldn't get service for several miles. Being upset, I finally talked to their tech support and was told that they use a combination of satelite and cell tower service and there was neither available where we were located. However, we continue to use it frequently, but have a concern that we could be in another remote location needing assistance and can't get service.