I bought a Nite Rider MiNewt 400 Dual in November 2009. Love these lights. 400 lumens on high and 200 on low. Run time is 3.5 hours on high and 7 hours on low. Low works just fine for commuting 95% of the time. High beam really lights up the road. This time of year I commute to and from work in the dark. In flash mode (at dusk or dawn) I have had car drivers yell at me to turn off my lights. I really feel a lot more safer with these lights. I paid $234 w/out tax at a bike store. My guess is you can do better than that online. The battery is lithium ion. Can take an hour or so to charge. Mounting is really easy and adaptable to different locations.

http://www.niterider.com/prod_minewt400dual.shtml