I noticed that after I had some skin problems on my face frozen off by the dermatologist and I haven't shaved for a couple of days, face id has slowed down a little. The amount of the slowdown is very small. I use the phone with two hands. Prior to this slowdown I would pick it up and point it at my face with my left hand and before I could get it totally in front of me and raise my right hand, it would unlock. Now I have to wait momentarily to swipe with my right hand. Not a huge deal but it its real. I suppose I could re-do face id to my "new" face but it's not worth it. I do have facial recognition off in settings.