I agree with you about not wanting to use batteries on principle, but I have to admit based on coming up behind other cyclists in traffic, that the battery-operated tail lamps with flashing LEDs are a lot more attention-getting.

Also, I suspect a lot of the variance in brightness from one headlamp to another rests with the quality of the reflector and lens. I don't have a lot of confidence in the headlamps I've seen that use a faceted reflector rather than a Fresnel-type lens.