Although previous generations of the Planet Bike rear LED blinky lights have mostly been just okay in terms of brightness, the most recent revision of that light (the Superflash Turbo) which I picked up this season is absolutely phenomenal. For a $30 two-AAA-battery unit - the cheapest of the cheap - this thing is bright beyond all reckoning. I always run it in its semi-random blink mode, which frequently causes trailing MUP riders to hit the ditch mid-seizure; cars typically move two or three lanes away from me to pass; aircraft overhead are forced to make course adjustments. Hyperbole aside, I've had numerous unsolicited comments from other cyclists, pedestrians and even motorists noting that the light is bright and visible to the point of obnoxiousness, even in broad daylight - which is exactly what I want from a rear visibility beacon. You can usually get quality if you're willing to pay for it, but sometimes the cheap stuff works just as well.