It could be the best new iPhone feature in years.
There are some limits to improve security, but the unlocking is almost as fast as regular FaceID.
It may not be the best solution, but its an effective one.

Complex, but Easy
Apple has really knocked this one out of the park.
In use, you notice nothing.
Just swipe up or tap your iPhones screen, and it unlocks.

Its very similar to letting yourApple Watch automatically unlock your Mac.
you’re free to then use it as usual.
However, because the watch throws up an alert, youll know about it immediately.
And the full-screen alert on the watch also lets you lock the iPhone remotely, which also disables FaceID.
Next time, youll have to unlock the iPhone with your passcode.
The exact behavior may change in future betas, or in the final release version.
For example, if you use Apple Pay on your iPhone, youll need your passcode.
If someone mugs you while youre using this setup, they can access your phone.
If your iPhone is lost, four- and six-digit PINs are virtually useless against current hacking tools.
Its far better to pick an actual phrase, containing numbers, letters, and typographic symbols.
And for unsupported things like Apple Pay on the iPhone, you could just use your Apple Watch anyway.
Out in the street, the difference could be huge.
This feature is going to be huge when iOS 14.5 and watchOS 7.4 launch.