Thought I'd share my experiences with XM radio.

Motivating story: Drove from LA to Vegas this past weekend. It was nice being able to listen to the same station the entire time driving through the Mojave.

Reception: Requires line-of-sight with the satellite, or it needs to be near one of the repeaters they've installed in urban areas. For example, I get no reception in my parking garage. Sometimes I'll get cut out for half a second when passing under a series of overpasses and the buffer runs out. But I've driven it all over California, and I've had no problems driving through the mountains.

Quality: it sounds good to me. They claim "near CD" quality, and it's true so far as I can tell. Even if it wasn't, road noise makes it indistinguishable to my ears.

Programming: Awesome. For the first few weeks I didn't know what to listen to, there is so much. One million times better than FM. I got fed up with hearing the same songs over and over, and 20 minutes every hour of commercials. Wide variety of options.

Sony has a "plug-and-play" unit (the one I have, btw) that enables you to listen in your car as well as at home. It's not a particularly elegant solution, but it works for me.

As for Sirius, they are fiscally, if not technologically, in worse shape than XM. XM has been running for about a year now, and Sirius is just getting off the ground. There is still an element of risk with both companies, since the subscriber base isn't growing as quickly as they'd like to see. This may turn around soon since you'll be starting to see them factory installed in new cars. Sirius was having problems with their chipsets earlier.

Programming-wise, I'd say that XM beats the socks off Sirius. I'll let you compare the channel lists for yourself though. Make sure you have the new XM list, since they've tweaked the line up a week or two ago

XM is cheaper, but has more commercials. I think Sirius is commercial free. However, not all XM stations have them, and most of the ones I listen to don't. Even the ones that have them have few of them, and aren't obtrusive. They're over before you realize you need to change the station.

Let me know if you have any other questions. I think it was some of the best money I've ever spent.