This bike light, at full power, is brighter some car headlights. Sometimes I worry about blinding cars as they come by (which is why you point your bike light DOWN, but still). I take the light off and put it in my pocket after riding somewhere. I've found this light as a flashlight INCREDIBLY useful in the most random and unforseen situations. A smartphone light can't hold a candle to this thing.
I mounted this to my helmet and I use this as a second light to supplement my handlebar mounted light. This light is perfect for early morning rides before sunrise where I'm tackling an hour long uphill portion or rolling flats of a mountain bike trail and by the time I get to the top, the sun has come up and I no longer need a light for the decent. It weighs so little it is perfect for my helmet and it has a low profile so it is less likely to snag on trees. For helmet mount just unscrew the clip from the handlebar mount, and use VHB tape to mount the clip on the top of the helmet. I tested runtime while on high and I noticed the low battery indication came on after 1 hr 40 mins, which is enough time for me to get to the top of a hill before sunrise. I attached 3 cell phone photos with this light only mounted on my helmet on low, med, high settings.