Except for the complete impossibility of having to deal with viruses. Ever. There literally can be no native stored code, and if somehow the running code does get infected, it's wiped on each reboot. For the user that wants those increase of ease over Android (which are significant when comparing mouse, flash, keyboard, etc) and over Desktops/Laptops (Chrome OS can boot by the time you open your laptop, meaning MUCH longer battery life by just keeping it off), not having to deal with virus's (at least, not without a major paradigm shift in the attackers methods which will happen eventually, but for now it poses a significant difficulty) capitalizes on the same market that Mac went after, but more effectively, as it really IS more difficult to write virus's for the ChromeOS than for a Mac (rather than just being unrealistic due to market share).