The application is currently available for PCs only; however, Amazon says, "Mac users – stay tuned. We’re working on a version just for you."
Amazon Cloud Player for PC brings music together from iTunes, Amazon, and Windows Media Player. It detects and adds new music to your library even if you bought it from iTunes or ripped a CD, keeping your music library organized and up-to-date.
You can also use the application to automatically export your Amazon MP3 purchases to iTunes and Windows Media Player. When you buy an AutoRip CD from Amazon a free MP3 version of the album will be instantly added to your Cloud Player for PC library even before your CD arrives.