I've been using a couple of Planet Bike headlights lately and I think the above picture conveys some useful information.
The light on the left is the Planet Bike Beamer 3. This little light runs on 2 AA batteries, comes with a nice handlebar bracket and so far seems quite waterproof and well-built.
The light on the right is the Planet Bike Blaze. The Blaze is slightly larger than the Beamer 3, seems similarly well-built and comes with both a handlebar and a helmet bracket. Like the Beamer 3, it also runs on 2 AA batteries.
Planet Bike lists both lights have having run times of "up to 100 hours". In practice, I've been running both lights with NiMH rechargeable AA batteries and I usually remember to charge them up about once a week or so. Depending on when I go to work, that means I may have logged a dozen hours of night riding in that week. For me, any light that can get me through a solid night of riding has a long enough battery life.
Basically the difference in the two lights comes down to beam pattern and price. I'd expected to prefer the pricier Blaze. As you can see from the above photo (shot in normal office light BTW) the Blaze has a stronger, more focused beam. The Beamer 3, which has three lower-powered LEDs compared to the Blaze's single 1/2 watt LED, has a more dispersed beam. The Blaze lets me see further down the road, while the Beamer 3 gives a broader view.
Now here is where I should put in the disclaimer that I have very good night vision. Some of my friends claim that I can see in the dark and while that isn't strictly true, I am comfortable with lower powered lights than what many of my rando buddies use.
I'm happy to navigate my commute with either of the two lights above, but my favorite set-up is what I have on my green bike right now: I have both a Blaze and Beamer 3 on that bike. On my little red Dahon, I've ridden the commute with a just Beamer 3 but I think I prefer the further reaching Blaze. Compared to my other favorite light, the Princeton Tec EOS, the light output of the Planet Bike lights is right on par. The beam of the EOS is probably about halfway between that of the Beamer 3 and the Blaze. The EOS has various power settings and more sophisticated circuitry,but the later generation LEDs and good optics of the Planet Bike lights seem to make very good use of the power they have. The EOS is super weather-proof, but the fact that it takes an odd number of AAA cells is still a little bothersome. The EOS and the Planet Bike lights can both be set to either flash or solid modes, but I find the faster flash rate of the Planet Bike lights to be better for riding.
Planet Bike has sent me fenders and nifty beanie in the past and they gave the Bicycle Alliance a good deal on Beamer 3 and Blinky 3 lights for our "Get Lit" program, but I've spent my own hard-earned bucks on the lights in this review. But I guess I am kind of pre-disposed to think favorably of a company like Planet Bike that not only makes good stuff, but also gives 25% of their profits to causes that promote and facilitate bicycle usage.