I've used this light for about a month, both mounted on my mountain biking helmet, and with the provided head strap. I'm very pleased with the 600 lumen output, and the fact that the light appears to have a very extended battery life. The light works well mounted to my Giro helmet with the provided hardware. However, my biggest disappointment is with the way it fits on my head with the strap. The coiled wire that runs between the rear light and the front spotlight is too short! Consequently, the whole assembly wants to ride up off the top of my head, unless I strap it around my head so hard that I practically get a headache. Why couldn't they make this wire an inch or two longer?
I'm also concerned about the durability and weather-ability of the charging port. I'm not sure that the plug would keep moisture out, especially given that it tends to pop out with motion and use. Once this plug is off thie port the internal guts don't look particularly durable.
In summary, this light is a good concept that needs a few tweaks to be an excellent product.