When Matias Duarte tried to unlock his Nexus Galaxy on-stage at today's Samsung event things didn't go so well. Some combination of his makeup and the lighting conspired to keep him from getting into his device, but after spending a little time with one ourselves we can confirm that it does indeed work -- and quickly. To program the feature, go into the settings and it'll train itself to recognize your mug. As it locks in a ring of circles frames your face and, hey presto, it's ready. After that you set up a backup form of identification and you're good to go.
Once it's ready we found it takes only a second or two to recognize and unlock the phone, meaning this should be even faster than swiping or punching in an unlock code. But, you still will need to do that from time to time, either when the lighting conditions are less than optimal or, apparently, when you weren't born with it and were relying a little too much on the Maybelline.