Same here. The first thing I noticed about my 5S was how bright the screen was, even at 50%. Add to that, the auto-brightness not seeming to work, I reduced the screen brightness down to around 10% and let the auto-brightness adjust the brightness up when i'm using it in the daylight. Not sure if the device is faulty or the OS is buggy because it doesn't reduce the brightness when auto-adjusting, but does increase when in a brighter room.