Perhaps a simple way to answer the question of "What's the big deal with gamma correction?" is to generate before and after images, as shown above.  Left image was rendered without gamma correction.  Right image was rendered with gamma correction.  Same textures, same lights, same render settings.  One can choose to furiously postwork the left image and it still looks ugly several hours later, or one can sit back and let Poser perform gamma correction to produce the superior image on the right.  It's entirely a personal choice really.