Studied about gamma correction and linear workflow at Digital Tutors few days ago..
Learned a bit on how to use Physical Sun & Sky in Mental Ray as well..
Without Gamma Correction
With Gamma Correction
Did you know that since how monitor interprets (shows) an image is difference from how our eye sees it, 8-bit images like JPEG, TARGA or BITMAP have been gamma-encoded to look proper?
And since Maya does not factor in your monitor gamma into lighting results, it is necessary to do some gamma correction in order to display proper colour!