Interesting article making a fairly reasoned case for a Windows and OSX desktop client for Google Music. There's an Android and iOS client, so why not a Windows and OSX client?
http://features.en.softonic.com/why-google-play-music-needs-a-desktop-client
BTW. Music Manager is still cr*p!
Android has a local player that can play music offline that is sitting on the android device. If that makes sense for an Android device, why doesn't it make sense for a laptop? And note again that Android can't use that NAS share either.
There are benefits to having everything in the cloud. But there are limitations too.