The cloud player could be better. But my biggest complaint is that Amazon needs to make playing music as ubiquitous as it makes reading books on the Kindle app. In fact, the one place I don't really need an app is on my PC (since I can just use the web version). I'd sure like to have a Windows Phone App and Windows 8.1 App though. And I'll bet there are a lot of people out there who would like an iPhone app or Google Phone app too.
If Amazon can make listening to music as easy on all my devices as it does reading a book, then they have my business. If not, I need to consider other cloud options for storing and buying my music.