Crazy bright. Has to be seen to be believed. It totally illuminates an entire broad cycleway, which has no lighting anywhere near it so would be pitch black. I can see everything, every bump etc. Charging is very convenient with the USB. Button is very tricky, borderline impossible with gloves on, but this means it won't get turned on by accident in a bag/pocket. Can't be more pleased. You won't regret it.
Edit: Lost a star due to battery life being far less than it should be, faulty I guess. Which normally isn't a problem, as you can get it returned/repaired.. unless you buy from Y-Frame Discounts, who will try to wriggle out of their legal obligations..