UPDATE:  Google have finally provided a native Linux client, just login to http://music.google.com/ and click 'Add Music' to install it. Last week I received a Beta invite for Google Music.  I jumped straight onto it only to meet the message "Music Manager is only available for PC and Mac".  Being an avid Linux user I was most displeased!  "Ok, no problem..." I thought and I jumped straight into a VMware'd Windows installation - no joy, it apparently doesn't support 'virtual machines' either. I stumbled upon musicalpha a Chrome Extension that looked quite promising albeit not quite complete (metadata not working). Alas, I had more important things to worry about and I gave up... Until today, I discovered that Ubuntu users had success running the Music Manager under wine.  One helpful guy even wrapped the binaries in a ZIP file you can grab from here.

Music Manager running nicely (under Wine), 4,712 tracks uploading as I type...