The chromebook is an online device. The music page is useless if you're offline :/
You upload the .mp3s to google's music page and you can access all those songs like iTunes or any other music program you're use to.
The music can be cashed on Android 3.1 devices and Ice Cream sandwich. I could see them allowing local HTML 5 storage at some point the same way it works on those devices..if you want to see it Youtube Google IO day one...it is about half way through.
cosmiconurb, how long did it take to load 4000 songs?
I've never loaded my CD's to my PC so I'm looking at a lot of work; should I begin loading them to my PC now, or skip that step and go directly to Google Music when I have an account?
It all depends on your upload. If you have 20 gigs of music, expect to upload 20 gigs of music to google. I have about 2.5k songs at the moment because I got tired of my internet being hung by uploading music.