Probably not real high on most people's list of priorities, but worth noting nonetheless is the fact that travelers are not allowed to make purchases from the duty free shop at ORD unless traveling on an international itin that day. Not that it's all that great of a shop (at least the one in T3; haven't been to the one in T5 in at least a decade), but if you're someone like me who enjoys buying hard-to-find and/or new fragrances, duty free shops are the place to do it. IME, the duty free shops at most airports (LAX and LHR immediately come to mind), allow all travelers to purchase anything except booze and tobacco, though you do have to pay sales tax if you're not flying on an international itin that day. Since ORD is my home airport, I'm annoyed that the one place I can't indulge is the airport I frequent most!