Hmm okay. I’ve never been able to make it work while lying in bed; I end up just tapping in my pin rather than fuss with getting it to go through.

I have the same problem. Recently realized it’s because I don’t wear glasses in bed and thus the phone is too close to my face for faceid to work

It works in pitch dark.

but it fails completely when you have a little bit of rain on your glasses :)

Depending on where you sit on the conscience/security sliding scale you might want to considering turning off “Require attention”. That solves 90% of glasses/sunglasses related issues.

Main issue for me in bed is failure to identify face smooshed into pillow. Raise head and unlock fine, even in full dark. Still requires neck muscle actuation that wasn't required with touch id.

For me it is because I don’t wear lenses and learned to move the phone a bit further away during the scan to make it eorl in bed. It works every time

I do it all the time, fwiw, but my girlfriend cannot get it to work reliably. So your mileage might vary, but in my experience ambient light does not matter.

Trueeee, when I bury half of my head in pillow.

No, but for me it often fails when outside in bright sunlight, especially if the sun is low in the sky, as it often is in my latitude. Perhaps it might work better if I try training it on my squinting face.

Sort of the same experience in some specific lighting conditions.

What I found out though is that it's because in such lighting conditions I don't blink, compounded by the fact that if it doesn't unlock I unconsciously keep on not blinking to... see it hopefully unlock! So when this happens I consciously blink and it unlocks immediately, which is kind of cognitively dissonant.

Unknown if that would apply to your situation, YMMV but I thought I'd throw this one out.

There's also a kind of annoying recurring situation where I want to look at stuff on the lock screen but don't want to actually unlock...

I do wish they'd have reintroduced Touch ID in the camera control button sensor (or just in the power button, as for the iPad Air) but I guess cases would cause a problem.