Advantegous mp3 is a free program that will undoubtedly convince you to only download music from Amazon MP3.

Though it may go against your long standing Apple-loyalty to purchase music from anywhere else, the promise of DRM-free music is an attraction all on its own.  Simply install the application, fire up the iTunes Store, find an album you're interested in, and select the “Get MP3 from Amazon” selection located in iTunes Script Menu to be directed to the album’s Amazon page.

All of Amazon’s MP3s can be downloaded to any digital media player and transferred to any computer, making iTunes seem like the alternative choice.

Via lifehacker