Jim, I don't need an instruction manual and many hours of learning time to use my headlamp. That comparison really limps!

I'm still trying to learn the intricacies of my camera (the other battery-dependent item I take with me). It went haywire on a trip last summer, and I didn't find out until I got home and spent two hours with the manual that the picture-taking mode dial had been bumped off automatic! I doubt that I'd ever be able to master a GPS, nor do I even want to try!