Seems to work well on mine
Sent from my 4G LTE Samsung Galaxy S III using Forum Runner
I understand smart stay keeps the phone awake while you are looking at it. If you look away for a couple seconds and it turns off, and then look back, will the screen turn back on?
I've found it works as long as you're holding the phone right in front of your face. It didn't work when I was looking down at the phone or like from an angle. It also didn't work for me in the dark obviously.
My guess: The front facing camera isn't the best, so if it can't clearly detect your face, it won't work.
I haven't looked for but also haven't seen the eye that said it turns off on my far less often now that its on and I wear glasses. Most of the time when it shuts off I have covered the front facing camera with a finger.