I've had XM since last spring and my main complaint with it is that they offer less channels in Canada than they do in the States.  It's nothing big, but it's kind of an annoyance. 
  
Even though I've since discovered Opie & Anthony and Ron & Fez and listen to at least parts of their shows every day, I bought it mostly for the sports, since it's hard to get a good signal on a station that plays Blue Jays games at night once the American stations power up.  I can barely pick up Ottawa AM stations and that's only an hour away.  Same goes for Leafs games.  It was really convienent on night shifts to go out on my break and catch a few minutes of whatever game was on, but I'm getting laid-off in a few weeks, so that won't matter anymore. 
  
The music stations are nice, but nothing I listen to that much.  I sometimes like to listen on weekends when the '70s and '80s channels play the old Casey Kasem countdowns, though.