I enjoy Google Play Music and use it daily (the paid version). I prefer it over Spotify/Rdio/Beats because it works better with Google Now voice actions, and I can run it well on every device I care to.

My remaining problem with it is their device limit. You can have 10 total devices, but you can deauthorize only 4 per year. This sounds like a lot but if you switch phones often or flash new ROMs you can use it up pretty quickly. In addition, if you upload music to the service the computer you use counts as a device. Once you're at your limit there's little you can do and you have no information on when you'll get a device deauthorization "credit" again. I had to call Google to get a one-time reset of my authorizations but it would be nice if they could modernize this some; such as by only using an authorization if you download music to the device for offline listening.