I had Sirius in my truck for a long time, it is great if you have really long drives or travel a lot for work. You don't have to worry about finding a channel and it is easy to turn on and off if you are getting in and out of the car a lot. I got tired of the stations though and even though it doesn't have commercials they still get in pretty good ruts with the music.
With that said I canned it when I was done with that job and have moved on to Spotify. It is 10 a month but it is literally almost every song in the world at the touch of a button. It works on my droid phone, computers, and ipad. It is basically like linking to an Itunes store but everything is free. You are essentially renting the music instead of purchasing. You can download them to the device when there are times you wont have internet which is cool. You can sync your ipod to it at home and download almost any music and then take the ipod with you. Buying one CD on itunes is more than this a month.
You can create playlists, search, star songs for later and play a radio station based on any song in the catalog. Anyway just giving you another option. They will just about give you a free subscription when you call to cancel though if you keep bartering with them. Sometimes it is fun to screw with them.