I wonder if it works with scarves and hats covering everything but your eyes. It seems like an obvious oversight, but it's a Californian company that launched a maps app without any transit support...
The keynote did say it works with hats, scarves, and glasses. It also works with face changes like growing out a beard.
It's starting to sound a lot like:
if (true) {
unlock_phone();
}
How about a big helmet? I imagine snowboarders/alpine skiers/motorcyclist will have to take off the helmet to unlock. As someone who goes snowboarding in the winter, it sounds really annoying to not only have to remove a glove, but also the helmet, to unlock the phone (or unlock with a passcode, which is still a downgrade from using the fingerprint).