Google demonstrated their Chrome OS again this past week where they indicated the OS will be essentially a gateway to the "cloud". For example, your files would be stored remotely in the cloud, not on a local hard disk.
If you think in terms of our current world where access to the Internet is done through an application on our computers, i.e., the browser, the Google concept for Chrome OS is somewhat foreign. However, projecting forward to Internet access being ubiquitous through many devices independent of a separate application like a browser, the Google OS approach makes sense.
Apple's success with the iPhone stems in large part from it being a consumer focused device rather than something made by techies with an engineering bent. Currently, the PC is still a techie device not a consumer device. The inner workings are too exposed to the user of the device. The Apple Mac computers are a step closer to a consumer device, but still too techie.
If we no longer think about computers as necessary for Internet access, i.e., we just use the services, the Chrome OS starts to make more sense. Is it premature in relation to the current mindset? Maybe, but the thought process behind it is definitely in the right direction.