I'll chime in a bit here...
If you are interested in downloading music... many of these services are free to access, and only cost money to purchase. If you are interested in iTunes, I suggest that you go to http://www.apple.com/itunes and download it for free and buy a song or two for a couple of bucks. Then compare with other services and if you like the selection/interface/sound quality.
The iTunes tracks are only 128k bit rate AAC, but they claim that they rip from the master tapes, not from CD. This should produce better quality, but I suggest you let your ears be the judge.
