At least with XM, you will also notice that the quality of some of the channels will go up/down depending on the daypart. XM holds several patents for their technology that allows them to dynamically allocate their bandwidth
Even as a shareholder, I cancelled my subscription when money became tight. I wasn't listening as much and a lot of the channels sounds like crap... particularly the traffic channels.
I found myself listening to MSNBC and even more of Bloomberg than anything else.