I use a NiteRider minewt.600 lumen light. So far it is great! Very bright and wide area of visibility. Did need to put a rubber strip on the bar mount for better mounting grip. But I love this wireless light.
I only use the light a 1/2 hr. at a time, but it seems to last a few days before I recharge. Sometimes I use it blinking, sometimes full steady light for night commuting. So I haven't kept track of how long it lasts before it needs a recharge.

I guess having a USB charger as well as a wallwart supplied with the light gives you another option for charging, which a commuter needs. I don't think anyone wants to carry their wallwart to work just for a recharge.