I have the Planet Bike 2W and the reason I don't use the strobe after dusk is that IMO fast strobing lights confuse cars in low light situations. I think drivers associate strobes with police and emergency vehicles. In the daytime it's not a problem but you need a very bright light to get drivers attentions when competing with bright sunshine. As mentioned, if you aim it directly at cars the central beam would seem very bright to cars at night. You can angle it slightly down at night so it isn't pointing directly at nearby cars. My own personal observation is that bikes with slow strobing lights (like twice a second) are best after dusk. Cars will key in on the light, but the flashing is slow enough that nobody will confuse you with an emergency vehicle. I started this thread to find such a light:

http://www.bikeforums.net/showthread...-2X-per-second