I keep gamma levels at default, especially when building and texturing planes. Hopefully X-Plane 10 will have better global illumination! Seems as if the sim gradually got darker from v6. I think X-Plane v6 had the best world lighting, ever since Ive hated the lighting with a burning passion! I think it may have something to do with how v9 works with contrast. Its really irritating! Even today if you compare X-Plane's sun to other simulators or games you'll notice that the worlds are much more vibrant. The key is the way lighting is rendered, it can make 3d involvement much more livelier. Here is a great example of great lighting!