I think using this plastic coating on the MBA is terrible. It feels awful to touch and its even worse to put on.
I tried it once and returned, not for me.
I take the view that these are devices that are meant to be used and in using them they do eventually show the signs of use. What they are not are museum pieces to be preserved in kevlar or plastic and opened with white gloves and treated with like a new born baby.
Honestly I think people that put so much effort into preserving their laptops, their iphones have a slight case of obsessive compulsive disorder taking pains to preserve the pristine condition of a unit they will no doubt sell as soon as the next model comes out. It is a fastidious addiction I have never understood.
I for one have never had a problem reselling anything I have owned and used for a couple of years. These things have great resale value and as long as you don't hurl them across the room and use them as a fly swatter your going to get a fair price during resale.