Google seems to pick and choose when they'll make a native app and when they'll go the web route with iOS. For Google Music, which is still in beta, they chose the web app route and it's actually still pretty good.
The promise of Google Music is that it lets you listen to music anywhere. Aces! Except, for all the unifying promises of its online locker, Google Music does kinda the same thing as your hard drive: It isolates your songs.