Having used Amazon Cloud Player quite a bit, as well as other similar web services (lala, grooveshark), I can say that Cloud Player is the worst web based music player I've used. Can anyone comment on Google Music, or iCloud?
Google Music works great at what it's intended to do. Play your music from anywhere.
That said, I've recently realized that I don't really like my music. That is, I'm much more interested in effective music discovery apps like Pandora, Grooveshark, and Turntable.fm.
Can't wait to see the Google+ spin on Google Music...
I just want apple to make my itunes collection available to me on any computer I'm on ... hopefully that happens sometime soon, so I don't have to pick the songs/albums/playlists I want to listen to that week and sync them to my iphone.