Finally started trying out Google Music Beta... I wonder how long it will take for my music to upload? There is no iPhone/iPod app yet and there doesn't seem to be an iOS optimized web site yet.
UPDATE: A Couple of days have passed and I already have ~1500 songs uploaded out of the 5500+ songs I have currently in my library. At this pace, my entire library could be backed up in the cloud in under a week. A screenshot of the web interface has been added to the photo gallery.