The iPhone X introduces a big change to the way you unlock your device in Face ID. Leveraging advanced facial recognition and the new TrueDepth front camera, Apple's flagship has no problem logging you in, whether you're wearing sunglasses or a hat. It also works well in the dark.
There's just one problem: Face ID is slower than what it replaces.
I've been using Face ID on the iPhone X for more than 24 hours, and I don't need a stopwatch to tell you that it unlocks my phone slower than when I was using Touch ID on my older iPhone 7 Plus. I used a stopwatch app anyway to prove my point.
With Face ID on the iPhone X, it took 1.2 seconds from pressing the side button to the iPhone X's screen turning on and for the phone to recognize me and unlock the device. And it was another 0.4 seconds to swipe up to get to the lock screen. Total time: 1.8 seconds. (You can simply tap the screen to wake it, but this took about the same amount of time).
On my iPhone 7 Plus, I could get to the home screen just by pressing and holding my thumb on the Touch ID sensor in an average of 0.91 seconds. That might not seem like a lot of time, but it adds up quickly when you're unlocking your phone dozens of time a day.
There is a workaround of sorts, though. You can swipe up from the bottom of the iPhone X's screen even while the iPhone X is looking for your face. Sometimes you might briefly see the word "Face ID" flash as the iPhone X transitions to the home screen, but you will still get to start using your phone faster.
It took me an average of 1.5 seconds using this method. That's still slower than Touch ID, but you will shave off a little bit of time.
Update 11/1: As John Gruber notes on Daring Fireball, you can save time by making sure Raise to Wake is enabled in settings and simply swiping up on the screen as you bring the phone to you. But this is still slower than using Touch ID. I timed it at 1.48 seconds if you include waiting for screen to turn on. It takes 1.16 seconds if you start timing from when the screen turns on.