I leave brightness and contrast on default. Backlight is max (142?) and currently outputgamma 1.8
You could mess with brightness/contrast but they seem kind of "destructive" in that they should degrade image quality. I wouldn't touch it unless I really wanted to raise the minimum brightness in bright environments, and I would start by raising outputgamma to 2.2 first (i.e. unmodified) if I really wanted that.
Thanks for this - I turned my outputgamma down from 2.2 to 1.8 and it looks way better.