Amazing, so bright on country lanes (no street lights), you can see everything. it is small, size of a large match box, lasts 3 hours full power, battery pack and cables are good, cables are a good length. the cables screw together, the old version pushed together, this is good on bumpy ground they don't come apart and leave you in the dark (this happened to a friend of mine). everything is good about this, apart from the head strap - a weird design, i can not get the thing to work as a head strap, tried every way - useless. on a bike's handle bars - fantastic. for the price you will not find better £200 in the shops.
Beware: it is blinding for car drivers, and causes them to slow down/stop - a good thing. don't look at the lights when working.
I use this for my Road bike and Mountain bike.