I've been using Amazon Music with my Echo devices for about a little under a year now. Overall its not a bad app, comparable in most ways to iTunes - the app has been refined considerably since its inception - its more stable than it was. Its still a bit hairy on the organization end, and uploading music from my own collections has been a bit problematic. Some albums won't upload completely, which is why I only give the app four stars. Its not as intuitive as some of the other music library apps available (again I'll reference iTunes) but when coupled with Amazon Prime and a subscription, the scope of the Amazon music selection is amazing.