I have a chance to test Google Chrome OS, thanks to people at gdgt who have packaged an image for VMWare for Google Chrome OS. You can download the image here and the instructions for using it here.
It boots very fast and it uses your Google accounts (don't have one? ). In seconds, it will load up with GMail by default and you can access more web applications after cliking on the Google Chrome icons on the top left (you may have to sign in again with your GMail accounts in order to show the applications below)
Here's the screenshot on my VMWare: