I like the gestures, but the unpredictability of when FaceID is going to work is maddening. Sometimes it works with sunglasses, sometimes not. Sometimes it works in the dim light of my bedroom, sometimes not. Sometimes it works when I absolutely don't expect it (half my face hidden in my pillow, towel wrapped around my face, complete darkness with face illuminated only by my lock screen) which only fools me into half expecting it to work when I shouldn't. Sometimes everything seems right, but it still doesn't work. I'm never completely taken by surprise because I'm never sure what will happen.
In other words, about a hundred times a day my train of thought is interrupted for a second or two while I stare at my phone and wonder if FaceID is going to work. This is a pretty terrible pattern of disruption. Technology should disappear into the background instead of inserting itself into the foreground of my attention every time I use it. The fingerprint home button was more reliable, and it was much easier to anticipate when it was going to fail because of a wet or dirty thumb.
When I am running and my hand is sweaty, it was impossible to unlock my old phone with fingerprint reader. Face ID works great in that case. I would say the fingerprint reader was the worst thing about my old phone. Granted I don't know how much better recent iPhone readers are in comparison but I expect they still have issues with wet or dirty hands.
That would be nice and simple if it were true, but it's not. Sometimes it fails when my face is fully visible. Sometimes it works when my face is not fully visible. It can work or not work with the same pair of sunglasses depending on... who knows? Maybe I'm just not smart enough to figure out the exact meaning of "fully visible."
Try retraining FaceID without glasses/headwear, when standing up and holding the phone in front of your face at similar height. Anecdotally, it adapts better to sunglasses/etc. that way.
Also when it fails with sunglasses, and ask for password the first time, immediately logging in with passport will make subsequent unlocks with sunglasses work better (presumably it marks that face adaptation as "correct").
In other words, about a hundred times a day my train of thought is interrupted for a second or two while I stare at my phone and wonder if FaceID is going to work. This is a pretty terrible pattern of disruption. Technology should disappear into the background instead of inserting itself into the foreground of my attention every time I use it. The fingerprint home button was more reliable, and it was much easier to anticipate when it was going to fail because of a wet or dirty thumb.