Last year I switched from using iTunes and Rhapsody for my source of music back to CD's. The main reason: convenience.
I'm switching again...to Amazon MP3.
They have a really good selection of music. Singles cost 89 or 99 cents.
The *big* difference over iTunes and Rhapsody: you download music as MP3, not a format that will only work on certain devices.
I have two iPods, an MP3 player for my car, phone with a media player, and my computer. MP3 is the only format that will work in all places (and any future devices I get). MP3 support is a requirement for me.
Anytime I bought from iTunes/Rhapsody, I'd immediately burn the DRM'ed songs to CD and then extract them as MP3's back to the hard drive. It was a painfully slow process...especially filling in all the missing information.
Amazon MP3 avoids all of this...I just pick a song and it is downloaded directly to my library AND it has all the song information and cover art!
Amazon MP3 is better than CD's because your purchase is immediate (no waiting for CD delivered by mail) and there is no need to rip the MP3's from the CD.
It is pretty addictive...I bought $40 worth of singles tonight.
If I can't find it on Amazon MP3, then I'll use CD's as my backup option.