I think I found out what's "wrong"  with Poserpro gamma correction and dynamic hair. Again I did some experiments today and I came to this conclusion (Please, correct me if I'm wrong because I think this isn't a simple problem): Gamma correction is meant to work with texture maps, to make the renderer work with lineair gamma decoded maps, and if I'm right it actually lowers the midtones of a texturemap before it's send to the renderer, and the renderer boost the midtones of the final picture to get it properly gamma corrected.
But dynamic hair doesn't use texturemaps, but a hair-lighting node. So in fact the gamma correction isn't needed for a hair node, and you have to decode (lower the midtones of) the hair-node if your using poserpro GC. 
This can be done the same way as BB does for his VSS-skinshader, by plugging in a power colormath node with a single add mathnode of 2.2 to value2, after the hair node.
You also have to reduce the translucency value, which a lot of dynamic hair shaders use.
If this is not clear, I can make a screenshot.

Best regards,

Bopper.

-How can you improve things when you don't make mistakes?