I've been a Sirius/XM customer for about six years, but canceled my service last month. Why did I cancel after all of this time? There wasn't a single reason, but the most important is that satellite radio is quickly becoming less relevant as a music delivery system.
With an iPhone and an iPod, I have a practically unlimited library of music that I can take with me. These days, most of my driving is local. The longest trip I'm likely to take is about 90 minutes, and most of the time, no more than 30. My car automatically syncs to my iPhone via Bluetooth and starts playing where it left off without my taking the phone out of my pocket. I download a lot of podcasts: science, music, news, politics, and the car is a good place to catch up on things. XM has a great variety of music, but the quality is lacking. I don't know if it has been decreasing or not, but my latest automobile has an excellent sound system and satellite radio doesn't sound any better than FM, maybe not as good on many channel. I've written to them about that and never received a response. The sound quality from my iPhone is excellent. Not only that, but if I want something more like a radio station experience, I can listen to Pandora, streaming over 3G. Even with their free service, the quality is still better than XM.
XM could have had other opportunities to rope me in. They offer an inexpensive Internet-only subscription. That, at least, would keep me as a customer. The only real negative I have to say about XM is that most of their news stations are commercial. I wasn't paying over $12 per month to listen to commercials; they could had their own commercial-free news station. For whatever reason they chose not to.