I've often been commuting with my lights on in the daylight this past summer and I've noticed something: I see lots of drivers approach an intersection as if they're going to roll through it, do a double take, see my high-powered-disco-strobe-flashing-annoying-front light and then come to a complete stop. Could be my imagination, but I think the lights make drivers notice this biker coming down the street more. It could be the reverse - it's me who's noticing the drivers stopping more because I know I have the lights on. They would've seen me and stopped anyway. I should probably do a proper scientific study. Maybe somebody already has. But in the meantime I think I'll keep riding with the lights on in the daylight.