It is bright as hell and supposedly has a 100,000-hour lamp life. They also claim that the batteries will last 4-times longer. If it lasts half as long as they claim, it will have been well worth the 9 bucks I spent.
These are both absolutely true statements, but also misleading. Yes, LEDs are far more efficient than incandescant bulbs and batteries will last longer for the same amount of light, but that's not the whole story.
As batteries drain in a conventional flashlight, voltage drops, wattage through the element drops, and the bulb intensity lessens exponentially as the tungsten filament cools. Since the conductivity of the filament is higher at low temperatures then when white-hot, electrical resistance drops, and more and more current is sucked out of the battery, leading to an exponential drop in light output and accelerated battery death. LEDs work differently, though- light (and power consumption) are a factor of voltage, and decrease linearly with the draining battery. As the voltage decreases, current decreases, too- so, as the battery dies, the light just slowly gets dimmer and dimmer, never really going out, but at some point gets to the point where you just replace the battery.
So, when you hear statements about LED lights going for hundreds of hours on a button cell without ever needing changing- take that with a grain of salt.
