Drunk people it works well on. I've strobed belligerent drunks before and it really does disorient them.
I did recently use a blip on someone, who I assume was sober(ish), about a year ago. I was by Midway Airport about 10:30 at night to pick up a friend from a late flight, when a 'friendly' driver was upset I wouldn't let him merge into the side of my vehicle. I honked at him and he was furious. At the next traffic light he rolled down his window to both give me a mouthful and the one finger salute. I ignored him, which made him madder, and he started to get out of his car. So I rolled the passenger window down and thinking he was going to get to scream some more, he stopped getting out of his car. He opens his mouth to utter another "Fuck You!" - and I blasted him with a 1000 lumens in the face from about 8-feet away. It had the desired effect it just reset him mid-sentence. The light turned green a moment later and I took off, while he sat there for a few seconds trying to figure out what had happened. I could see in my rear view that his girlfriend was laughing at him as I drove away.
I haven't had a lot of instances where I find light to be the most useful tool, but that certainly worked. I think it's really both a matter or surprise and expectation. He was expecting me to engage verbally and instead just got hit with blinding light and the next thing he sees is my tail lights vanishing in the distance. If I hadn't been using a powerful flashlight at relatively close distance, it would not have worked nearly as well. The fact that we were on a fairly poorly lit street with minimal ambient lighting also contribute to the efficacy of it, I think. The fact that we were both in cars, so our night vision was adjusted to low ambient lighting inside the vehicle, the way light bounces around inside of a car changes those dynamics too.
Anyways, that is my single anecdotal, "I've used a flashlight on a sober person once to reset them" story.