[I have no idea what people think is so great about it, .
Using a Surefire 9P or a 6P plus extender, you can use AA when you run out of CR123s when the end of the world is 'nigh'
Yes it will work. No, you won't get full-output. It will be dim and constantly dimming, because it's just direct driving the emitter, and makes no difference whether it's a regular version, L, LL, or LLL. I have no idea what people think is so great about it, but have to admit I was pleasantly surprised by the initial output on fresh cells when I tried it. Quite usable around the house.
Runtime will depend on the batteries.