For those of you pining for the best quality music, like I try to get, here's something you may be interested in. For me - CD quality is what I'd like to have everywhere I go. A lot goes in to what you actually hear though. The source material is absolutely critical. How it gets to your amp, then how it gets to your speakers and finally what the speakers are capable of reproducing compared to everything else. So here's a website with a test you can run for yourself and what you listen with.
A set of browser-based ABX tests comparing lossless and lossy music samples
abx.digitalfeed.net
An article I found was using the highlighting the Spotify test - but I found this list. Doing the test, you are trying to figure out if X is either the A source or B source. If you play A then B and don't hear anything different, you're not going to benefit from what some call HD Audio.
I remember the old 128-bit MP-3 compression having some kind of artificial sound added to it. Seems 128-bit compression has grown up. Of course, there's a lot more to it than just the bit rate.
Edited to add: I've been using Amazon HD for a few months now. I download the music to save on my data budget for when I'm out and about. The app is certainly lacking in management, I'll give you that. But the added library of "unlimited music" is real nice to have compared to standard Prime Music.