Google Music would likely also include social networking features and P2P services. Intriguingly, the search giant is trying to let each customer listen to the whole song once before purchasing (30-second samples would be available after that). That's similar to how Lala worked before Apple bought it and killed it.
We can see the advantages of having our music hosted in the cloud, but an important question will be whether the service will let you upload songs you have already purchased. Furthermore, how much storage would this digital music locker have? Consumers will likely have a lot of questions, but before that, we're sure artists, labels, and publishers will want to know how much of a cut they will be getting. In other words, the details are still up in the air, and if this service ever launches, chances are it will be quite different than what we're hearing about right now.