They work better as a secondary device for power users but I suspect the number of people who can use them as a primary device isn't negligible and will increase as the platform matures.
I have mostly retired my Chromebook for a higher spec laptop running a full linux desktop. But I can see a lot of potential for Chromebooks and with some nicer models coming along with access to the Android store I can see them replacing both laptops and tablets for family.
They are secure, practical and low maintenance and I am not at all surprised that they have done well in education and I expect higher specced ones have a very good chance in enterprise.