Runtime was 13 hours of good light - after that the final descent into darkness began, with substantial dimming by 13.5 hours, at which point I ended the test and popped it on charge (1A 5v charger with Europlug - I assume charge voltage is controlled by PCB inside). The red led on the charger goes green after about 4.5 hours - and you're then good for another 13 hour burn. It doesn't appear to be regulated (regulated output is a feature, by the way, that I consider to be vastly over-rated and gimmicky because of the flat discharge curve of li-ion. Besides which it adds unnecessary complexity).
4 little leds serve as the (very dim but probably endless) low-power mode. Switch is Off-Main-Off-Low-Off-Main-Off-Low etc so you get darkness between modes.
The optic gives the slightly warm-toned emitter a soft-edged spot which is larger than some, with a fairly bright area around the spot. Further out, the spill gets very ragged and ringy, with a narrow ring at the extremity with rainbow chromatic aberration. Does the untidy spill matter? Depends how fussy you are. However, the spill can be improved a lot by experimenting with little pieces of tracing paper applied to the front of the lens. Given time you can arrive at an improvement that softens the spill while maintaining most of the spot's throw.
In the beam shot comparison below, the untidy spill of this compact lamp is seen on the right, with the excellently smooth spill of the "Yellow and Grey" Chinese lamp previously seen on this blog on the left.
This is a very compact lamp, weighing in the hand about the same as an Oldham headshell although having a smaller diameter. The mounting blade is excellent and highly adjustable, with the hinge secured by a massive screw with locknuts. When the unit is mounted on the helmet, it's easy to run a bootlace around it and pass through a hole in the helmet so you don't lose it if it falls off. It's also trivially easy to make a strong diy lanyard securing tag that mounts on the hinge bolt.
Waterproofed to withstand sprayed water and heavy rain, but not total immersion. A bit of insulating tape here and there could probably make it dunkable. I wasn't able to examine the guts, because the casing had been glued shut, which was a little disappointing. There appears to be a rubber gasket between the bezel and front lens, which is reassuring.
Conclusion: a little (but only a little) expensive at £45 + postage considering the untidy beam, but it still gives out plenty of caveable light for 13 hours. Compared to some of the over-priced competition like the Troglite (about £60) this is a good value lamp. Excellent U-fold mounting blade for caving helmets - as good as it gets. Despite the beam, this is a better buy than most "elastic strap" headlamps. A little thoughtful waterproofing work on the kitchen table (kid's non-setting modelling clay rammed into the screw holes and insulating tape around the bezel/body join etc) and you're good to go in a fairly wet cave. What else? Light and pocket size. The charge voltage of 5v is a bonus, because you can probably charge via USB and various cellphone car chargers (as yet untried).