"Insight Refugee" nailed it ... the biggest pro to having the OnStar hotspot is that the cell antenna in the car is much more powerful than the one in your phone and will have reception in the more "sketchy" areas that your phone may not (YMMV depending on area). Right now I don't have it enabled - either by itself or added as a device on my Mobile Share Plan on AT&T but on our next long road trip I likely will as there are areas that we'll drive that I know my phone won't get reception but the car likely will.