I had a three months of free XM Radio when I bought my Saturn Aura last summer. I liked the variety but hated the sound quality. Since I don’t do long trips in the car much a subscription wasn’t worth it to me.
They just gave me another 2-week free trial. I tried listening to it again. I like most of the stations in the 40’s, but every one of them sounds like a compromised internet radio stream. The highs are compressed and warbly like the 128kbps MP3 encodes I made over 10 years ago. It’s pretty sad. Unless you’re doing regional driving and want consistent stations I can’t see why you’d want to compromise on sound quality so noticably vs. FM/CD/MP3. The convenience, metadata, and variety of XM are good, but the listening experience isn’t worth it to me.