I found this light on sale for a fraction of the listed price (which I could never afford), and decided to purchase it for those **very rare** occasions when I have to do a longer night ride.
Since I haven't had the opportunity to use it so far, I will limit this review and some tips to what I found when I took it out of the box and tested it.
First thing to do is charge the battery before first time use as done with a cellphone or any device like that. Installation and plugging together is pretty straight forward. A broad Velcro strap comes with the kit to attach the battery. When I connect the light to the battery it flashes briefly once, and the two buttons light up.

Oddly enough, the instructions don't tell how to turn the light on and off and change the settings. As others already pointed out, the left button turns the light on and off. The right button changes the three brightness settings (low, medium, high); and after holding it down for a few seconds changes it to blinking mode. Once it's there, another click changes it to SOS blinking (which I find really neat!!), and the next click brings it back to steady.

Pros: It's seemingly well made, small, compact, and relatively light weight. It's easy to detach, and both light and battery are small enough to fit in a fanny pack or saddle bag- definitely a plus since I wouldn't let it on the parked / unattended bike! The housing is all aluminum, which is important as the light gets warm really fast. Having one button for on/off and another for changing settings is a BIG plus! The three brightness levels cover every situation- the low setting is similar to the average battery operated head light; the medium is really nice, and the high is extremely bright- I plan to use medium and high as low and high beam on a dark road; and the low setting for well lit streets. I would be careful with the (very fast, almost strobe-like!) blinking mode, and advice against using it at high brightness- I got dizzy when I tested it, and there are people out there who are susceptible to fast blinking lights. The SOS mode however makes a really nice emergency light, and is definitely a plus.

Cons (and suggestions for improvement): The (aprox 4') cord might be a tad short for some users, and having a pouch for the battery would be nice. Also an in-line off / on switch so the light doesn't have to be unplugged every time between uses to avoid draining the battery.
A real disappointment for me was the head mount. I was planning on using this light when I have to work in dark, confined spaces (which I do very often), but since I cannot point it up- or forward- only down at a (at least for me) unpractical angle, I will use it on the bike only... for which it is primarily intended.

Overall, this seems to be a really nice light!

This light is so bright it's unbelievable. I have a very nice stream light flashlight and this is just as bright if not brighter. For the money it is really a great buy as most lights this bright are much more expensive. I was worried about the dispersal pattern, and while it is like a very large, very bright circle with a slight halo around it, having this mounted to my handlebars made the entire trail in front of me Light up bright as day all in the central bright area and the halo was just a little lagniappe. I am riding on a windy trail on a levee along the Mississippi River so I really did my research and comparisons before I made the purchase as I didn't want to fall in or become gator bait. This light is like a headlight and exceeded my expectations. It also has a very white color to it on the brightest setting which was useful. I passed a snake on the trail and not only could I see it from a distance but I could also make out the colors as if it were daytime. This is the only bike light I've used in the past 15 years but in the pitch black, surrounded by river and farm fields, this thing was an absolute wonder and I can't imagine needing a brighter light or a wider beam for any normal activity. The mount is going to take a little tinkering though, and as I can't easily mount it to the center of my handle bars, and it doesn't pivot or swivel, and my ocd cannot have an off center light guiding me..I will have to get creative with how I am going to mount this thing in a way that it will be centered and not move around when I hit bumpy trail (I was, however, riding a road bike on a gravel road so I might as well have had wooden tires..my teeth were all but chattering from the vibrations so I'm not surprised the light was shifting a bit. When I got to paved trail it was completely steady. All in all this is a light firstly and they definitely focused mostly on that, which I am not upset about. It seems sturdy and the battery mount is excellent. The headlamp accessory was a nice touch too though I haven't used it. I also noticed this light lit up reflective road signs that it was not even pointing at from about 75-100 yards. It's a lot of light, and I do not regret this purchase one bit.

I took a friend out to go on a night ride. This was his first time and this kid is super fast on the downhill. I let him borrow this Very Light you may want to buy, and I told him keep going , I will catch up eventually. With that said.........my friend who never did a night ride before thought this light was Friggin amazing. And the funny thing was he was on the LOW setting when he first initially descended down the hill.....this trail has a lot of switch backs and we did 6 miles of up hills, and I told him in the beginning how to go from low to high , but he left it in low .......now he told me while flying down the hill in LOW setting , he wished it had a brighter setting , so he F around with the button on the right and realized, Holly S this light is way F brighter than I thought and when he went to the brightest setting he was like..........holly S and was flying even faster........i can not compete, I go up the hill , I go down the hill, and this light works well for me, but my friend was like.....holly S .........this light is really awesome. Folks, buy this light . My friend is friggen awesome when going downhill , and for someone who NEVER went night riding before he BROKE the Sound Barrier, ........

I purchased this bicycle headlamp about a year ago. I fiddled around and never used it for it's intended purpose, riding my electric unicycle at night. Tonight I finally took the handlebar mount off the bottom and mounted it to my helmet with velcro. I was so impressed with it. It has 3 settings, low, med and high. Low is a little too dim, medium is sufficient to ride up to about 25 mph and high is fantastic and good for 30+. Button to change between settings was easy to quickly access. This allowed me to run it on high then quickly click it to low when encountering people on the trail. Mounting on my helmet allowed me to direct it away from people which helped to not blind them. Having no strobe mode and the select button separate from the power button makes this light super functional and easy to use.
Couple of cons. The charger has no lights to let you know when it's fully charged or if it is even charging. The light pattern is a little too unfocused so it can be fairly easy to blind other people with it. Aside from those two little nags, I can't recommend this light enough. I'm super impressed and very happy with the purchase.

I've had this light for a few months now and all I can say is that I'm highly satisfied with this light! I commute 10 miles to work and needed a better light for the dark early morning rides. Not only can I see the road better, the bright light makes me more easily seen by car drivers. I use the strobe option for daytime riding coming home or just running errands around town. Before, even using my old strobe, I'd have cars cut me off in driveways or turning at intersections. Not anymore! I've not had any more cutoffs since using this light.

My battery pack seems to last a while. I can get at least three commutes before having to charge again. The mounting bands don't seem to hold very well on bumpy roads, but that's to be expected. I don't use the battery pouch; I just put the battery in my frame bag. Do keep in mind that there are lights in the selector buttons so don't leave the battery pack plugged in or it'll drain the battery.

Overall great product. I'll be buying another for my other bike. Might even buy a third and make use of the headband for nighttime trail hikes!