Is this ability truly worthless, or is it only worthwhile against PCs? i've heard conflicting reports...

it would be nice to know, so i can take it off of my action bar. :-)

and to the person that said that they can see the hidden a little better with it on: You can see most  stealthed NPCs anyhow. if you want to see them better, use flare. at least flare works like it is supposed to. :-)

Also the REASON i know you can see stealthed NPCs is i play with a guy that is legally blind, and even he can see the shadowmaw panthers and shadowcats that are around, at the same time i do, without me using anything at all to track/unhide them.