Well the other thing is that the Core i5 and i7 models have had acceleration for AES encryption built into the instruction set (AES-NI - see: http://en.wikipedi

Well the other thing is that the Core i5 and i7 models have had acceleration for AES encryption built into the instruction set (AES-NI - see: http://en.wikipedia.org/wiki/AES_instruction_set http://en.wikipedia.org/wiki/AES_instruction_set) since the 2010 MBPs (Core i3 processors were excluded). So it's fitting that the FileVault speeds on the 2011 MBA with the i7 is much better than the C2D.