Google Chrome

Well I meant the hardware, these are only the first generation of Chromebooks, they will improve the hardware.

But, that aside, you just answered your own question, kind of. The cloud improves all the time, so your experience improves 'in real time'. Also the software that is on the machine automatically updates*.

*according to this rather nice video anyway:

Doesn't matter if the Could is the most advanced technology platform in the Universe if you've got no data connection though.