Gizmodo are right about the feature set difference, but they have compared the Macbook Air and the Asus EeePC in terms of size. It comes off pretty well, because even though it is twice the thickness, it is way small in all the other dimensions. What does this mean? Well if you want a machine that does web, email and to be ultra portable then there is personal opinion between which one you want.
If you want full size capability and the very same software as you have on your main machine then you are looking at the Macbook Air. But then, I have another machine for that.
The other thing is to compare the price… the EeePC is at least a quarter of the price of the HD model, and less said about the flash model…
