Self-explanatory. I've considered using it due to the minor annoyance of trying to take out specific NPCs in the dark, but so far, I've only ever used it once.
TBH, I don't find it all that useful, honestly. Plus, I could see it giving away your position in PvP, so that might be another downside. I know you can turn it off and all, but still.
First poll, please don't hurt me...!