This is an excellent light, one of the best I've had. It has several settings, from steady to flash and is VERY bright. Great for visibility on those dark commutes. The battery life is good; I have been getting about 6 hours per charge.
I purchased this rear light because I have had good luck with Nite Rider products previously and I needed a new rear light on my commuter bike. I particularly like the fact that it is visible from the sides much more than most lights. Several different blink modes. I like the one that modulates more than strobes. Very secure mount that is still easy to get on and off fast. An added bonus is that it is also daytime visible. I've had it for a couple of months now and use it on my daily commute. It is good for 3-4 hours at least, but I can just bring it in to work and plug it into the USB on my desktop if I need a quick charge.
Light is awesome from the view point of visibility. Definitely one of the more visible lights amongst the group I ride.
Has a slight drawback in that you have to remove the entire light when you go to recharge and requires recharging after each ride. Granted our rides are three hours in which it does hold the charge without fail.