I was an XM Radio subscriber for a couple of years but I shut it down in 2008. I was getting more enjoyment from my own music selection of MP3's and felt XM wasn't worth the ~$14/month I was paying. Now I see the Frankenstein company Sirius/XM (or whatever they're called) is planning to offer a Sirius app for the iPhone.
I already enjoy plenty of free radio stations through the iheartradio and AOL Radio apps. If I'm able to pick up a satellite radio signal (i.e., not on a plane) I'm also able to get a cell signal. This app certainly wouldn't cause me to consider renewing my old subscription. In fact, if you have an iPhone I don't understand why you'd bother with satellite radio at all. Nobody listens to Howard Stern anymore. I'm surprised Sirius/XM is still in business.