A very interesting discussion has started in the graphics card forum about some leaked NVIDIA drivers (revision 185.20) that adds a new feature called “ambient occlusion”.  This enhancement apparently is adding some nice visual lighting effects but causes a lot of stress on gaming hardware; HonestJohn saw his Far Cry 2 performance go from about 60 FPS to 45 FPS with the option enabled.  There are screen shots included in the thread as well.

NVIDIA Beta 185.20 drivers add "ambient occlusion" - Graphics Cards 2
Ambient occlusion is a shading method used in 3D computer graphics which helps add realism to local reflection models by taking into account attenuation of light due to occlusion. Ambient Occlusion attempts to approximate the way light radiates in real life, especially off of what is normally considered non-reflective surfaces. For example, in the way light through a small crack in the curtain in an otherwise darkened hotel room can slightly illuminate the entire room, and not just the path of light passing through the crack itself.