The PB 2w is a great light that gets good run times on rechargeable batteries and compares nicely to the 25lux Lumotec on my wife's bike and puts out similar light to a 10watt halogen... the strobe function is seizure inducing.

I picked up a set of these MEC USB Plasma lights and am quite pleased at their use as marker lights... they are pretty bright in either direction.

MEC Plasma USB front light