Lights without batteries; that’s what I’m talking about. And not those faint lights with whirring, tire-rubbing bottle generators from decades past. I’ve been using the Supernova E3 and Shimano Alfine dynamo hub for about a year, and I love both of these.
The E3 is a ~300 lumen 130 gram beauty, machined from 6061 aluminum. It uses a Cateye style clamp which allows for a decent pivot range. During a recent off-road commute detour, I was able to pivot the light to illuminate upcoming turns. It features a “stand-light”, which means it continues to glow for a few minutes when you stop, despite not having a battery. 300 lumens is about 100 more than the Dinotte 200AA I reviewed last year. While using this light, I’ve been mistaken for a motorcycle, complimented, and cars respectfully yield to me more than ever. You can actually see the road with this sign; it’s not just a faint beacon. If you need more, there’s the E3 Triple with 800 lumens of battery-free goodness.
The Alfine front hub (3D72) is an Ultegra spec 6W generator that can power lights and devices. I had it built up by Anthony at LongLeaf using a stout Velocity Dyad 36-hole rim, good enough for mountain bike duty on my 29’r. It features a centerlock disc-brake rotor mount, and a solid connector for the light. I’ve taken this wheel on and off countless times, and the connector hasn’t ever slipped off or loosened despite all the jostling. At walking speeds the light begins to flicker a usable amount of light, and at what feels like 5mph the flicker becomes a solid beam.
Even beyond commuting and touring, there’s been discussion of using the Alfine and E3 for ultra-endurance racing like the Tour Divide ~3,000 mile race from Canada to Mexico. It beats carrying batteries, worrying about running out of power, and using much dimmer headlamps.
I love this setup. I have no complaints about it, and I love not having to worry about carrying charged batteries. It’s liberating to jump on the bike and ride with hassle-free illumination for the next 5 or 5000 miles.
Bike Denton 
I’ve had the same hub for about a year too, but with the cheap Shimano light. My wife has the setup with a planet bike light which is amazingly bright. It would be astounding that these aren’t on more bikes, except for the fact that you can buy a decent bike for the price of the wheel and light.
The E3 is even 5g lighter, now you HAVE to upgrade!