Interesting that the two reviews I've read about Chrome OS (PC World and Engadget), mentioned the hardware reminded them of the black Macbook of a few years back.
I think this could be an interesting development, because it would make the "network computer" finally come to life. In order to succeed, it would need pervasive, fast, Internet connectivity, but that's happening. 4G cellular networks and Internet access on planes are being implemented rather quickly, so you can get an Internet connection almost anywhere, and the network computer (and ChromeOS) begins to make sense in that scenario.
If you throw out the cost and overhead of Windows, along with the headaches to manage it, the "netbook" becomes even more affordable and isn't just a small laptop anymore. You can probably get good performance out of a dual-core Atom processor and Broadcomm HD accelerator chip with ChromeOS. I'm really interested in the security features, and the ability to pass the computer around to others while still protecting your data.
However, IMO, the biggest obstacle to success is whether or not the user truly trusts "cloud computing" and Google. If there's any doubt in the user's mind that their data can be compromised or sold, ChromeOS won't take off.