In reply to zimpara:
I've never used the Ion, but very much like the E+lite. I would say they're a little different in concept.
THe E+lite really is a spare only sort of thing, its fine for close up work and in a tent, but quite low powered for navigating. I have, though, used it for whole weekends when I've forgotten the Myo, and its fine, still better than a Petzl Zoom! It really is tiny, and the weight is almost unnoticeable, so it lives inside my first aid kit. Batteries are a little harder to find, but still common, and seem to last a good length of time. The way it switches on and off, allowing red only use, is useful.
The Ion packs quite a punch at 100 Lumens, and on paper seems to beat the E+Lite. OK its twice the weight, but that's still only 50g, and it only looks a little bigger. Batteries common too.
I reckon if its purely as an emergency back up, the E+lite will still be best, but if its for occasional use as a proper headlight too, the Ion looks good.