I never used much physical media (napster generation), but I still keep a local music collection on hard drive. I tried cloud options but it's simply a horrible experience when travelling, which is where I spend most of my time listening to music.

General problems that aren't going away soon are the latency between clicking next and the song starting is way too high, especially annoying when you shuffle through a few songs at once. And I've only got 2GB of data a month, so I need to cache locally anyway, killing most of the benefits. The absolute worst thing is that you're tied to the shitty players that cloud-music companies produce.

Some google music specific problems were using tonnes of data even when I'm just playing cached files and things like hitting the next button twice in a row will give random results depending on which web request comes back first. I'm sure it works fine on the google campus though.

For the foreseeable future I'll be sticking with poweramp and music on SD.