When I first got my Sirius system, I hated it. Sound quality was horrendous (this was in Oct.). However, they've recently upgraded their codecs, and wow... I am their biggest fan now. According to most people I've talked to, both XM and Sirius have very good sound quality. Sirius, however, sounds a little better, fuller, not as flat as XM. Plus, Sirius allows a lot more detail in their display. XM will display an artist like Christina A (they have a very small max display size). Sirius can go a lot further (I think they max out at 256 characters). Both XM and Sirius have great programming. You'll never go back to regular terrestrial radio every again (I haven't listened to a local station since I got the system). Sirius got rid of their 90's station, which sucks since that was my favorite station, but they may add it back. Sirius has better rock and electronic selections, as well as eclectic fair (bluegrass, anyone?). XM has solid programming all the way around. This friends and family deal is sweet. Definitely jump on it. I paid like $400+ for my entire system. Oh, if you went to CES, you'll know that they will release home versions of Sirius this year. They also demoed video through existing equipment. They were able to broadcast 2 channels with no loss of sound quality to any of their radio stations. It's just proof of concept, but it's pretty freaking cool. Anyway, if you're a music snob and remember when radio and MTV were pioneers of music, instead of regurgitating popular music, then get Sirius or XM. You'll never go back.
What I listened to today on the way to class:
Extreme - Mutha (deep cut off one of their earlier albums) Big Rock Station
Frou Frou - forgot the name, but you won't hear Frou Frou on any local station
Warrant - Heaven
Orbital - More electronic music