The app is quite fully featured as well. It allows you to access all of your own music that you may have purchased or uploaded to Google's cloud. And, the app allows you to use your All Access pass to stream any of the other 20 million tracks in Google's database. You can stream if you want, or save music to your iPhone for offline playback. Music can be played back at 320kbps and can be played back through any AirPlay or Bluetooth devices. There is also the recommended music lists (both algorithmically generated, and curated by humans), and the Radio feature which works just like it would with Spotify, Pandora, or iTunes Radio, although Google lets you add and remove tracks from the radio playlist, so you have a bit more control.
Google Play Music for iOS doesn't have everything though. As you would expect, the restrictions that Apple has placed on apps means that there is no way to purchase new music, or even start an All Access subscription through the Play Music app, but if you buy something on the web, it will sync to your iPhone. There are also a few smaller missing features like the "I feel lucky" radio option, but Google says it is working on bringing those in a future update.
On a smaller note, you'll see that the iOS Play Music app uses a new flatter looking logo for the service. We expect that will filter across to Android soon enough.
Download: Google Play Music
source: The Verge