I seem to be like many of the others, During the regular hiking season, I do carry the Petzl E-light, and a spare coin battery for it, however I really don't use it a heck of a lot. I have hiked at night with it, but find that I don't acutally *need* it most of the time to do so, and even then I usually only use the little red led in it to avoid demolishing my night vision.

Having said that, that's pretty rare. Most of the time I only use it to read a book at night, or occasionally to find something while in my hammock or tent at night. I could probably do without it if I were going totally minimalist, particularly in the summer. I don't because I like to read, and it weighs about an ounce (I tossed the useless case). I used to carry a "backup" led light but decided based on the above that I didn't need to anymore.

In winter I carry a nice bright Tikka Plus with Red filter, and a small high intensity flashlight. Winter up here means 18 hours of darkness, so you end up doing things in the dark and I find I want a bit more light then.