Same here, I added a second Cycle Torch "Night Owl" headlight. I like these because I can charge them on the USB port of my computer, and they stay charged all week. They are apparently water-reppellant and cold reppellant.
I also had to replace my "Monkey-lectric" M-210 for my rear wheel, these illuminate the bike very well during the dark days of winter.
An added benefit is that both products tend to be on sale right about now