ICON Irix II

For the money, I think this is one of the best headlamp deals out there.

The Good: Variable power output is selectable via a rheostat-type user interface. Simply turn the top dial to turn it on, and keep turning it to increase the brightness.  This is easily the best user interface I have seen, and I wonder why almost every headlamp doesn't follow its lead.  

The lowest setting is just enough to see around camp or inside your pack at night without upsetting your night vision.  On high, it puts out close to the claimed 50 lumens.  The beam is basically pretty floody (30-35 degrees) but has enough throw at medium to high power levels to light trail markings on a tree that is 30-40 yards away.  

It runs on 1 AA.  80 hours on low, about 2.5 hours on high.  Rechargeables work perfectly, if not better than alkalines.  It's cheap.  Plenty bright for almost any trail use on high.  Has a battery cap that will lock the light off so it won't get turned on in your pack.

The Bad:  Not a lot of throw if that's what you're after (I wasn't so I'm pleased with its output).  Not fully waterproof, just pretty water resistant.  Fits loosely in the brackets on the headband, so it can come out easily, or not hold its point of aim. Does let a little light glare back at you from the tip of the led emitter lenses.

Quick fixes:  To tighten up the light in its bracket, just wrap a strip of duct tape around the light body at each contact point to make it a bit larger diameter.  To fix the glare issue, a small fold of electrical tape will shield your eyes pretty effectively.