Pain in the butt I think, if you need to flash your lights whilst they are on you have to switch them on and off quickly, otherwise you just full-beam the oncoming car! Very easy to forget and just blind people.
Im with the lights on 24/7 concept. Proven to be safer if you have at the very least your sidelights on during the day (although its not known exactly why, but thought to be due to the fact that a frightening percentage of drivers have deficient eyesight, theyve got more chance of spotting you with your lights on)