I've contributed this comment before, and may sound like a broken record to those who've seen it already, (and I hope these aren't famous last words, knock on wood, because there aren't any guarantees about this):
Time and time again, at least once a day on my commute, I've noticed distracted, cell-phone-talking, coffee-drinking + smoking, texting, headphone-wearing, etc., etc. car drivers perk up and notice my "annoying" headlight modulators. Blind spots: If I'm not in their blind spot for even a few seconds, and then go into it, they seen to have spotted me in their mirror, know I'm there, maybe can't quite tell if I'm a cop, or whatever, but they seem to take a second look and they see me. Cars at intersections sometimes start to roll, then hit the brakes and wait as I go by. So far, that is.
And, as others have posted, it's a very useful habit to watch head movements, and front wheel movements also. Years ago, with my first two bikes without a modulator, but with an always-on headlight, my experiences were identical to the posters above; close calls happened a lot.