XM Radio
I work a circuit city so i deal with XM and Sirrus satelite radio, and i also am a XM user for about two months now.
I have had no problems with mine. You can puchase a seperate XM reciever to hook up to your head unit which is the $300. unit everyone is looking at. it works like an FM modulator on a cd changer.
the other option is a head unit that has a tuner built into it, sony, kenwood, alpine all offer these on there higher models.
The only problems i've heard are with the portable units, apparently they can't pick up a signal well on water.
I pay just a little more than $10 after tax a month for great un interupted music. I've never realy liked radio talk shows but i've found my self listening to them more and more on long trips. I heard soon they will start broadcasting movie and tv show audio, kinda bringing back the old days of listening to Dr. Demento on the radio as a kid.