I've been researching recording options today and found the following:

Audio Hijack Pro $32 Mac (record anything that connects to mac-even camcorders and analog vido, imovies etc), splits clips when gap between songs (customize), audio from favorite movies onto ipod
No, it's limited to whatever the receiver can output, so just like any other Sirius radio, it records one channel at a time. But you can give it a list of artists or songs that you like (which you can add to all the time) and it will record only those artists or songs. You can also give it a list of artists you DON'T want it to record, and it won't record those. Then just click Record, let it sit overnight, and you'll have a directory of MP3's from only your selected artists.

But by far the greatest thing is that you can set it to not record anything less than say, one minute long - which means it doesn't record commercials!! So when it's on a talk station, it records the show, and skips the commercials!

for a PC I'm surprised noone suggested Timetrax. If anyone uses these please comment.