Everyone cried about the fingerprint sensor of the note 8, which was located right next to the camera on the backside. However I never had issues unlocking my phone. Usually worked on the first or second try.
I love that the sensor is now behind the screen but very often I reach my 5 unlock attempts and get locked out. Even tho I have added the same finger multiple times with different positions.
I've noticed if I have anything at all on my thumb it won't read my print at all even if my hands are just a bit sweaty. I usually just wipe my thumb on my shirt first and it works first try every time. I also noticed if I don't have a screen protector at all it will work even if my hands are a bit dirty so I'm guessing my screen protector must be interfering with the sensor.