Summary?

1. Gamma correction is the correct way to adjust the input colours and textures used in a render, and the output render itself, for display on a computer screen. (Actually it's a very close approximation, but close enough to pass for correct nearly all the time). 

2. With GC rendering, the 'old' method of making a Poser render look sort of okay by adding more lights to brighten up the dark areas is no longer necessary. Also we no longer need to use those shaders that have been unrealistically adjusted to try to compensate for the lack of GC (e.g. by adding a faint ambient glow).

3. Therefore, if you use those 'old' light sets / shaders and gamma correction, you will have far too much light in your scene, and textures will be blown out.

4. Poser 8 includes Tone Mapping with an option for HSV Exponential. This is an approximation to 'proper' input and output gamma correction.

5. In SM's view (I would guess) the full ramifications of using proper GC are just too confusing for the average Poser user, so it will remain a Pro feature.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)