It makes me grin, when they flash me. That means that they really did see me. You don't want to blind them, though. You just want your lights to be annoying enough not to ignore. You may consider using a dimmer setting, if you are going to point that light at their faces. I point my 130 lumen handlebar light right at eye-height for most drivers, and point my brighter helmet light at the road in front of me. I've had many fewer close calls with people turning in front of me since I set up my bike this way.