I've never used one, but it seems to me that it would work very well in a stressful situation.

As a species, rifles and handguns are the only method of launching a projectile in which we DON'T focus intently on the target.

Look at what human beings have always done--throw a rock, look at the target. Throw a spear, look at the target. Atalatl, look at the target. Shoot a bow (traditional) look at the target.

Try to hit a nail with a hammer while looking at the hammer.

Toss in a lot of stress as in a self defense scenario, i.e. somebody shooting at you, and I'd wager there's way less than one shooter in ten--if that many--whose focus is going to be on the front sight and not the threat. As a species we've survived because we could focus on and deal with a threat.

We'd like to think we could do it, but in those high stress situations human nature is going to take over. Putting an aiming point or reference on the target works with the way people deal with stress and danger.