Jason Snell, over at Six Colors, has written about his experience with the iPhone X during the past week. One use case where he felt the phone wasn't as usable as previous models was when trying to operate it while it lay flat on a table or desk:
Facing straight up, the Face ID camera can’t see me, so I can’t unlock my phone without leaning way over the table or picking the phone up. And attention detection can’t detect me, so after 30 seconds the screen dims.
I hadn’t realized how much I left an iPhone unlocked on a table for a minute or two. The iPhone X is more aggressive about locking the phone (and dimming the display), and Face ID is no help. I suppose in the end, the phone will train me—but right now it’s one of the areas where my old way of using my iPhone no longer seems to apply.
The iPhone X can be unlocked with a passcode instead of Face ID, but it's not obvious how to do it. To use a passcode, tap the screen to wake up the iPhone, swipe up on the Home bar, and tap Face ID.
I do this to unlock my iPhone while it's lay down flat on my desk.
The aggressive screen lock is something I ran into even when I unlock with a passcode. The default setting for Auto-Lock seems to be 30 seconds, so I've changed that to one minute and it's feels much more usable.