Just got an invite to Google's service. Complete crap. Music uploader pegs your CPU at 100% while it takes days to upload your music--this is not an exaggeration. I'm cool with the upload time. It's a lot of bits. The CPU pegging isn't kosher, though. Had to completely uninstall it from my PC. The browser-based player is okay, thought it craps out if your bandwidth or CPU is otherwise being sapped (i.e., when you are running the uploader). Also degrades over time.
On the bright side, I got a few new songs out of it.
Personally I'm gonna pay those evil bastards at Apple some more of my hard earned money for their Music Match service. I've been meaning to re-rip all of my 160Kbps MP3s, but I have many hundreds of CDs, and $25 is worth it to me for magic 256K conversion. And you get the music in the cloud to boot. May drop it after the year, though. We'll see.