Hey mate, just my 2 cents.
I got one over a year ago. Not used it for a while now but the times I did use it I liked it alot. You go the option of using two lights like you said, plus you get an extra battery storage device that can sit on the headband or go into a bag etc. The top band stops the thing from slipping down over your eyes which is a big plus when you're climbing, running etc.
The light holders can be moved around the headband to point in different directions relative to the direction in which your head is pointing, they can also be elevated/depressed so you can tilt the flashlight(s) up or down. I find two flashlights overkill (I just tilt the one I use according to my needs) but the option to have two is pretty nice. The band is designed to fit the L(AA) and P series lights but can fit larger ones to a certain extent.
I've not put mine through any really tough activities, but its served me well for what I use it for.
Rich.