I've had one for several months now. I carry it on a keychain, more as a novelty, than anything else. Most of my friends think I only go for the high powered stuff, so they are pretty impressed when I show off this tiny light.
I don't use it a lot, but I have only changed batteries in it once in the several months I've had it. I do use it at least every couple of days for a short time, just to make sure it's still working or to show off. I'm not really sure I needed to change batteries when I did, but I just couldn't believe the original set of batteries had lasted so long.
It doesn't put out a lot of light, but in a dark room, you would have no problem walking around without tripping on something or banging into something.
For it's size, it's almost a must carry - both for novelty value and as an emergency backup.