Great question Chris, As i layer up terrain with textures and deformers etc and objects etc. I find, and also in various 3d apps I use, that doing some lower level brighter colors enhance the overall ambience and sunlight (or placed lights) that comes into the scene, most of the time its real subtle, but it gives images depth and a more warm feel, if you're doing a sunny type scene. In a dark scene I use the same method but use variants of grey and blues to enhance the lighting, it saves a lot of render time once you get a method of your liking down.
