I decided to give this neat little free app when I first got my iPod touch two weeks ago (you can stream online as well). In all honesty, from a music standpoint, I think the music quality rivals or bests Sirius/XM (which I also have). Unfortunately, it doesn't have the content stations like MLB, NFL, Stern, O&A, etc, but it's really a nice music service. You can even stream it in your car with their car kit. Anyone else using this? http://www.slacker.com/
I love it. I have it for my BlackBerry. For MLB I have an app that is quite nice and I can listen to either teams announcer and watch clips after the game if I want. With slacker on the phone I can cache a station so that if I am out of range I get continuous music until I am back in tower range. The wife is paying for the premium version and she really loves it.
I chose Slacker over Pandora for more skips per hour. If you are in a 3G area it is bad a, but I only wish you could stream the music and use other apps simultaneously rather than having to leave up the Slacker App.