One of my holiday gifts to myself was a copy of Dark Shader, partially because I was sick of using notepad and in part because I was curious about the shaders it came with. The one I was immediately drawn to was the water color shader. Below you'll find two screen shots from FPSC of the same scene, the first without any shader effects, the second using the water color effects shader included with Dark Shader.
I was pleasantly surprised by the shader's in-game performance, there was only a frame-rate drop of ~10 FPS.