If you look at app data for play music, it APPEARS to be saving music - I currently show over 700MB of data for the app. However if I open the app and select "On Device" instead of "All Music", I there is never anything listed (In Listen Now, My Library, etc).
So it appears to me that songs are cached but never used for anything, meaning I'm re-streaming every time I listen to something. It definitely appears that way when I re-listen to playlists.
Anyone else notice this?