Add me to the long list of people (according to the reviews) that cannot get Amazon Music to work. It cannot download my long playlist, but it does download Amazon's playlists. I'm an Amazon Prime customer in the United States. I guess I'll have to download music to my phone directly. I guess that's why USB exists.
But what I'd REALLY like to listen to are Audible audio books. I can't find any sort of app to play them in the store. Is there any way to play them on the watch?