Face unlock works when your eyes are closed (ugh)

I guess if you keep secrets from your significant other on your phone, don't get A P4 until they get this fixed.
 
The biggest issue with this for me is that Face Unlock won't work with any banking apps, etc. until they update, which according to AC, almost no apps have yet. So you will have to enter passwords, etc for most apps regardless of Face Unlock for a while.

From AC Review.

Despite how awesome face unlock is, it has limitations that are incredibly frustrating. The technology is clearly sound and secure. But face unlock's problem isn't technology, it's app developers. In order for an app to be unlocked with the Pixel 4's face unlock, it has to be using the latest "BiometricPrompt" API — any app that uses the old API for just fingerprint sensors will not be aware of face unlock, meaning it falls back to prompting you to log in manually with a username and password.

Not a single app that I use with a fingerprint sensor today has face unlock support.
None of the apps I use that typically require a fingerprint have been updated with the BiometricPrompt API. Not Bank of America, American Express, Enpass, PayPal, and on down the list ... not a single one. This API has been available since the Android 9 release was finalized, and yet only a handful of apps are using it. Google points out that Dashlane, Keeper, Password Safe, Robinhood, and 1Password all use BiometricPrompt ... popular apps, but c'mon, it's five apps.

Right now, it's incredibly frustrating to be using a brand-new $900 phone and have to sign into my password manager manually (remember, it doesn't support face unlock either!) and use its autofill service to log into my secure banking and payment apps; something you don't have to do on a $100 phone with a fingerprint sensor. This should be a short-term problem, though: all apps that want to release an update after November 1 must target the Android 9 API level, including the new biometrics API, which should make quick work of this problem. But that doesn't force developers to update on November 1 — we could be waiting months to see many popular apps, particularly from the big companies like banks, update for face unlock.

Everything else aside, this may be the biggest reason to delay buying a Pixel 4 — you don't realize how frustrating it is to be missing fast biometric authentication until it's gone.
 
For those worried about it, before going to sleep, lock it down and problem solved. It will require a passcode to unlock when you wake up.
 
Personally no attention awareness does not bother me but ‘months’ to fix it did surprise me, that indicates that it is not straightforward at all.

As mentioned above what does bother me is that this will have an impact on how quickly face unlock is incorporated to apps e.g. banking apps may not be happy to use it without some kind of attention awareness. Months of apps not supporting face ID would be very annoying!
 
I’m more annoyed that only like 5 apps support the face unlock API than I am about the phone unlocking with eyes closed.
 
I saw some reviews that it unlocks at times you don't want it to unlock. Like glancing at it to check time, see a message on the lock screen, etc.
Which then forces you to lock it manually again.
How would the device know when you want to unlock or not unlock?
 
I'm happy that its going to unlock when I look at it when my transition glasses are dark as sunglasses because I am outside. If it has to see my eyes to work, then that's a fail for me. I have a S9+ with iris scanning and it almost never works because I wear glasses.
 
How would the device know when you want to unlock or not unlock?

It opens every time regardless, whenever you look directly at your phone. I read that Apple has a further swipe up required after it unlocks, but Pixel unlocks opens up immediately.
 
It opens every time regardless, whenever you look directly at your phone. I read that Apple has a further swipe up required after it unlocks, but Pixel unlocks opens up immediately.
Yeah... I checked into it. That can probably be changed but not sure I have an issue with something like that. It's not much difference than having smart unlock on.