Reception is never an issue with the Sirius in my GTI. Don't know about sound quality, as 99% of my listening is talk radio - CBC, BBC and NPR. I play CDs when I want music.
Then we got the Yukon with XM. Reception cuts out all the time in the mountains, but I can't say if that's an XM issue or a GM-antenna issue. XM didn't even have CBC (they do now, but for extra $), so would have cancelled it except that my wife still wanted it.
Like quad said, if you're willing to spend a few minutes on the phone you can get them cheaper: I'm paying ~50% of the posted rate for each.
Even then, I'm not sure how much longer I'll keep subscribing. In the car, I can get CBC over the air just about anywhere. We used to listen to Sirius at home, but net radio is just as good - and free.