Comparing Google Chrome OS with Windows 7 is apples and oranges.
Google Chrome OS is basically Google Chrome, and that's it. It's perfect if your life is on the cloud - all your photos, documents, etc etc - and you don't use any programs that aren't web-based (although admittedly web apps are starting to give most desktop apps a run for their money, like grooveshark, atrium, etc etc) .
But if you want to save your files to your hard drive, have a music collection, a catalogue of movies, or install any program then it's not possible to use it as your primary OS. Great for a laptop perhaps.