Your Tivo won’t record the XM channels? That doesn’t surprise me, as more and more content owners are getting persnickety about the use of their stuff.
Windows Media Center won’t play back certain channels on DirecTV because they’ve been flagged by the network as non-recordable, but I can record XM radio just fine.
I know there are other programs out there that will capture audio streams, so you could record XM online.
From my experience though, XM is a great way to get exposed to new artists, and then just go download the full album (through legitimate channels, of couse).
I need to do a comparison, but I’m pretty sure that a ripped MP3 will have WAY better audio quality than what you can record from XM.