I've had XM for nearly 3 years now. I have three older Roady2 units, two in cars, and one in home. Here's what you can expect with the XT, which is essentially similar but thinner and sleeker:
Audio quality ranges from pretty good to low-bandwidth. In a car environment, it's not that big of a deal sinceyou're dealing with road noise, etc. At home, you'll note some hiss and artifacting on the worst channels (usually those in the channel 200 and up range). Music channels are actually very good to excellent. If you use a direct connection to your XM radio instead of the built-in FM modulator, the sound improves even more.
Delphi sells a kit for $29 at Circuit City and other retailers that adds a better modulator mounted in-line with your car's existing antenna. Yes, you still need the XM antenna, but the sound quality is FAR better using this unit and you don't have to worry about "splatter" from strong radio stations using the same frequency (this helps a LOT when traveling city-to-city, where an open frequency in city A may have a 100,000 watt blowtorch in another city). A bonus in that kit is an additional cigarette lighter plug, which you can wire into your fuse panel, plug your XM auto power adapter into, and discreetly hide the entire works. Makes for a nice custom installation (I've done 3 so far and they look/work great).
Can you use this thing in your home? Yes. With a caveat. You MUST purchase a home kit for the unit. Not terribly expensive, but it adds flexibility and allows you to get more out of your XM dollars. However, I'm a lazy SOB, so I bought another Roady2 to use in the house. Bonus: that same FM transmitter used in the car, built into every RoadyXT too, allows you to listen to your XM indoors and out, as long as you are in range. I love being able to listen to MLB while I'm mowing, without having to blast a radio. I can work outside, or work out, and stay up with whatever game i"m following.
For more on programming available with XM, check out www.xmradio.com. You can even sign up for a free listen online and check out the music. And remember: the holidays are fast approaching. This makes a pretty neat gift, as I gave one last year to a family member who LOVES it.
One last thing: Sports programming on XM includes MLB, NHL, NASCAR, college sports, and they had outstanding World Cup coverage, live. MLB gives you the home broadcast of the team hosting each game. NHL is the same, so if Pittsburgh is in Chicago, you'll hear the Blackhawks announcers. For some this is an issue; in that case, get NHL online and listen there. Note that even though TV may be blacked out for MLB games due to territorial or broadcast restrictions, you ALWAYS get the audio feed, no matter what. In the insipid world of MLB, I live in Orioles territory (even though I'm 6 hours away from Baltimore, only 5 from DC). Yet I cannot watch a single Nationals game on TV, ever... they're blacked out here. But with XM, I can listen to any game I choose. MLB TV DOES observe blackout rules, so be warned. Just because you're watching online, the same territorial restrictions apply.
I'll respond to any posts I see asking for more info. Give it a try: you've spent $59 on far worse in your life.