I don't have the ability to use gamma correction myself, unless I do it the hard way, so I was kinda waiting for bagginsbill to show up. However my popcorn has all gone now. :)

Fortunately aRtBee raised the point that was bugging me, but I lacked the experience to bring up myself.

Quote - Photoshop CG does the GC-job after rendering only, Poser Pro GC performs a pre-render anti-GC as well.

In short: gamma correction in postwork is only half the story. You need to un-correct your maps for the render maths to work properly. This is why I don't do the job manually. ;)