I've had Sirius for quite a few years, both 'in car' and a 'boombox', and I love it! I use the boombox in the house, work shop, and outdoors. And since I've had it in my cars, I never listen to AM or FM anymore!
The car that I have now came with both SiriusXM and OnStar. I subscribed to both at the end of the free trial period, and also kept and extended the built-in cellphone. I've used the OnStar a few times for directions, and have been satisfied. I've also used the phone a few times. As for the SiriusXM, it allows us to listen to just about any ballgame we want to, regardless of where we are, and to all if the NASCAR races too. Add to that, the news and talk stations I enjoy are on there too.
I like the assurance of knowing that if I'm in crash, I don't have to rely solely on my cellphone to call for help. I've been in a wreck that there was no way possible for me to find or use a cellphone! Because when an object that is in motion comes to a screeching, crashing, extremely sudden stop....stuff inside the vehicle gets RADICALLY rearranged in very short order. And sometimes even objects in clothing pockets cannot be accessed because if the new shape of the vehicle's cabin. OnStar would have certainly been a blessing at that time.
I'll keep my OnStar and SiriusXM for as long as they are available. YMMV