A buddy of mine got the iPhone X. He likes the screen size, but is still getting used to the fact that for the facial recognition to turn it on, he has to pick it up, bring it up to his face, and stare at it. That doesn't appeal to me from a UX perspective.
Another application of the face-rec technology is games. Developer Nathan Gitter figured out how to make a game that you play using your eyebrows. I can't tell if the game—which kind of reminds me of "Frogger"—is fun to play or not, but watching him play it is hilarious:
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It would be funny if all the top players of this game wound up with really wrinkled, wizened faces.
iPhone X users that want to give it a try, the game is called "Rainbrow."