Out of sure curiosity I downloaded the Hexxeh build (http://chromeos.hexxeh.net/) and installed it to a USB drive.
I am extremely impressed. If all you want to do is surf the internet it is perfect. I am going to hang on to it just for that purpose.
It is slow on my laptop (Acer 5532 3GB RAM) for some reason. The keyboard lags for a moment or two before the text appears on screen.
On 1gb of ram with a much slower processesor desktop it works wonders, using it to type this right now.
It will never replace Windows (or Mac) for hardcore computer users. But for light users that just want email and other internet applications it is really nice and fast.