Google Music went live for U.S. users today, leaving the invite-only beta announced this summer. It's free, and it lets you host up to 20,000 of your songs and stream them to your devices. You can also "pin" songs from the player, which will cache them on your device for playing offline.
You can also now purchase music from the Android Market. It's available in high-quality, 320kbps MP3 format, and you get a 90-second preview before you buy in the store. But to drive more sharing and purchases, the service is integrated with Google+. Music that's shared to Google+ can be played back in its entirety by anyone in your circles.
Facebook is a social network bigger than most countries, so Spotify's streaming-only music business has a scale advantage. But Google Music offers something no other social music service does: full-length, high-quality playback for all your friends on Google+. Google Music is a compelling offering, giving users a 20,000-song streaming locker for free, and the Android Market music store has lots of discovery features. Would a great music service like this drive you to use Google+ more?