Hello All, I would like advice from the community to see if buying a used 64GB or 128GB SSD, 2GB, 1.6 C2D either 2009 or 2010 macbook air model for $500 or $550 is worth the purchase? What do you think? The apple site is still selling this model for $699. Thanks!  I'll mostly be using it for documents, illustrator cs5, and some matlab.