Re: the eye, think I meant someone else actually? Doesn't matter, really.
I'm going to have to go with placebo effect. If there is any extra input lag from v-sync, I'm willing to bet it's unnoticeable in a blind test. I'd be more concerned with network latency or a host of other issues first.
No way would I trade a millisecond for the eyesore that is v-sync off. The screen tear would cause me far more problems than imperceptible amounts of time.