Went to the apple store several times this week in Albuquerque. I literally tried just about every iPhone 5s and a few 5c models they had on display to see if their sensors were off. Every single phone I tested was off. Tested flat, all were off anywhere from -2 to -5 degrees. Tested on the side(SIM card slot), all were off from -3 to -5 degrees. Tested standing right side up(charge port on the bottom), all were off from -1 to -3 degrees. Only one apple genius out of 3 that I talked to who actually owned the 5s himself was aware that it is an issue. And yes I did feel awkward going from table to table testing the sensor problem, but anything for science! Lol