On a dedicated commuter I would love to have a dynamo based system feeding into a rechargeable, with easy to replace cells, battery pack that could either be recharged from the dynamo or plugged into a A/C recharger. Also include a usb recharging point so tourers could use the system to charge usb devices like gps, ipod, phones etc. Say 400 lumens or so front and maybe 100 lumen rear. (your choice of modes on both front or rear; high, medium, flashing) Pay some attention to making the led's upgradable to newer versions that will allow higher output for the same voltage. I also like the option of a lower mount point in the front. I think you get a better throw, it keeps the handle bars cleaner and reduces bumping and jaring the light head. Maybe a mount off the front brake boss to position at the lower end of the head tube.