What might these "system specific enhancements" be exactly? http://support.apple.com/kb/DL1712 EDIT: To address all the speculation below: this link is the SAME update that Late-2013 MBPs get automatically in their update app. Apple posts the updates online also. Please stop with the confusion! The only point of posting the link was to reference the fact that the newest rMBPs got their OWN update, for the vague reason of "system specific enhancements." .