I'm about to buy Macbook AIR. This will be my second mac machine owned in a long time (first was G4 12in laptop). Before I make my purchase, I'd like to ask a few questions. I know Macbook Air is built like tank with no flexing because it's made out of a solid aluminum block. However, I must question the toughness of the said material...Is there some sort of "coating/finishing touch" on the pure aluminum material that could warrant possible wear downs in time? Fade,discoloration, ect.. From looking at the units in Apple Store, Air seemed like to get scratched rather easily on the bottom.. What your verdict? How is the finishing? Do you think invisibleShield will be a necessity? Any other problems using the machine? Fan noise? Heat? How do I manage them to an acceptable level?