Let me give a great example of where I see FaceID being a hinderence. Sitting down at a dinner table at a restaurant with others, phone's in pocket. I need to unlock it and check something.
TouchID: As I pull my phone from my right front pocket, my thumb touches the pad and has already authenticated, and the phone has already loaded the home screen. By the time it reaches my visible area below the table out of view of the other guests, I can check my item.
FaceID: (assumed until I actually try it) As I pull my phone from my right front pocket, I must click the power button on the upper right on the phone to wake it. I then must bring the phone into view of my face, most likely above the table to get the correct angle, therefore showing my phone being used inconsiderately to other guests, then once I look at the phone (however short it is), I then must swipe up on the screen with the same or more likely, other hand. I then can bring the phone back down below the table to check my item.
There are 2 additional steps in FaceID vs TouchID. The power click, and the swipe up. This cannot be faster than a single push of my finger upon a sensor which does not necessarily have to be aimed at my face. Imagine this scenario in a meeting, in a theater, on a date, heck I definitely don't condone phones and driving having CarPlay, but it's easier in a car to unlock. I again reserve my true final comments until after Friday when people actually start using the phone, and I'm not just trolling as I bought two of them with the intent of hopefully upgrading my 7 Plus to one of them. I'm just seeing real world situations where FaceID scares me.