I've got to disagree with tsl on this one. I've run a generator system for the past 5 years and I've been quite impressed. I started out with a Supernova E3, original series, symmetrical beam. While brighter than the 13W halogen L&M Solo I was using, it wasn't a perfect solution because of the symmetrical lens; a lot of the lamp's oomph was lost to skyward scatter.
After a year or so, I traded up to an Edelux; what a difference from a symmetrical beam! Most of the light is focused where you actually need it; *on the road.* There is minimal upward scatter, the same way that an automobile headlight works.
I had some issues with the Edelux though; mostly 1st gen design problems which have been solved. But in the mean time while mine was off for repair, I tried a B&M IQ Cyo and I've actually kept it on as my commuter and rando lamp. It's got the same innards as the Edelux, but a plastic housing with an Alu heatsink top instead of the Edelux' design of using the entire lamp housing as the heatsink. The effective losses are not noticeable in light output.
In riding 300 and 400k brevets where I've been out in pitch black national forests doing 12 mile descents on rutted service roads in the rain, I can't say I've ever been disappointed with my generator lighting.