10/10 I wear a pair of polarized Maui Jim sunglasses. After getting my X this morning I tested FaceID While wearing them. Full sun. I tried it with the sun in my face, at my side, at my back (so it was shining on the phone and I would’ve been backlit). I tested it in the car (so I was covered in moving, partial shade), and while in my car in complete shade, all with the polarized sunglasses on. It worked every time. The times in the car, my phone was not held directly in front of me as the steering wheel would’ve been awkward, so I held it as I normally do, which is off to the side a bit. So far, FaceID is a champ.