Personally, I've never bypassed those who have been waiting for their proper turns just for the sake of saving time, which the OP seems to suggest. I have walked around someone at the X-ray who was taking an unreasonable amount of time to organize their belongings onto the belt, which I think is okay to do especially when the person is clearly a casual traveller in the expert lane, but I would never cut the entire line, even if I might miss my flight as a result.