Or Android, since I do believe it's been on there awhile too. Damn, this is awesome. Even in areas where I know the towers are switching, and/or I've got lower signal strength, the music never glitches. It's a very nicely designed UI, and is easy to navigate quickly at a stoplight.
As for the service itself, I've got the $20 a year plan which includes 20GB of space for general stuff, but your music (whether you bought it from Amazon or not) doesn't count towards the limit. So I've got my entire iTunes catalog uploaded, as well as music application installs, photos, etc.
It's a really good deal, IMO. The Amazon Cloud Player app itself is free, of course. If they end up coming out with a Prime Video player, I'll definitely jump on that too.
The only place where they're lacking is their clients for cloud storage. The Amazon Cloud Drive app for OS X is Java-based, and it doesn't do syncing yet, like Dropbox. If they get that taken care of, as well as come out with an iOS client app, I'm likely going to switch to Amazon for all cloud stuff.
I've been using this for a while. The app can glitch when signals get REALLY bad, but otherwise it works well.