Three big updates: (1) Their web-based cloud player is now “officially” iPad friendly; (2) all past purchase through the Amazon MP3 store can now be stored for free; and (3) you now get unlimited music storage with any paid storage plan of the cloud drive.
In short, for as little as $20/year you can store every single song you’ve ever bought from Amazon as well as any other MP3 and AAC music file you have on your computer. Not a bad deal.