I've been fiddling around with the settings for a while, and finally settled on something I like so far.
For reference, I've got both the in-game brightness and gamma set at 1.0, and I'm running on a laptop with an Intel 915 GPU (meh).
Hard light: R-0.3 G-0.1 B-0.2
Desaturation: R-0.5 G-1.0 B-0.7
Glare strength: 0.65
Glare Size: 6
Darken Sky: on (for some reason, though, turning this on turns off my terrain detail textures)
I'm also running the game at 16-bit, with "force 32-bit" on both blur and post processing.
Looks good to me, but it may be a little dull for others. One man's dessert, and all of that.