Thanks Garilla - LEDs have come on leaps and bounds in the last few years.
The turbo setting is too intense for traffic, so I'll run it at high or medium and save the wall of light for country lanes/off-road.
It's a thrower, but the beam has bright spill too - it's good for the roads when you're travelling at speed. I've submerged the torch in the sink and there was no water ingress.
I'll have to see how the run times go, but I'll carry spare batteries for longer rides just in case.
It's a bit top heavy (good heatsinking) and 18650 batteries are not to everyone's tastes, but it's a lot of lumen for the money. That said, I don't think I'll get another as I can't see how I'll attach two of these monsters to my bike!