Awesme - I have the Magicshine MJ-872, which is the same as the 870 except it has four emitters instead of three (rated 1600lm against 1200lm). I hardly ever use it on full power, so the 870 should be plenty bright. Second, it's quite "floody" - giving you a LOT of light all around, but not casting a particularly long beam. It's like driving your car with the lights on dip. But in practice, even riding down a steep hill at full speed in complete darkness, it provides enough light to see the road surface in time to avoid potholes or broken glass, and it lights up reflective signs a long way off. However, I still feel a little insecure at speed, or in traffic, so I use it with a 170lm helmet-mounted light that has a very tight beam (LED Lenser H7), so I can "look around" and flash cars to let them know I'm there (cars really do dip their lights at this setup!) I also have the Magicshine MJ-818 tail light which is 85 lumens - as bright as the brake-light on a car - and shares the same battery (comes with a Y-cable). I use it on steady when it's dark, so it's not so blinding, and on flash in daylight. Finally, I've got the six-cell battery (the standard is four-cell). So far I've used the setup for up to three hours - mostly using the 872 at half power - and the indicator on the light tells me I have half the capacity remaining. If you're interested, there's a nice dissembly test of the MJ-870 and 872 here: http://www.light-test.info/index.php?option=com_content&view=article&id=103%3Amagicshine-mj870-mj872-cree-xp-g&catid=34%3Arowerowe&Itemid=55&lang=en
