A tester :
The improved XML contains:
Better Physics
Bloom
Improved HDR
Better Textures and mapping
Better Rain and splashes quantity
Improved Reflections in the water and for the cars
Better Water, Vegetation and Geometry quality
Improved LOD and FOV
Better colors everywhere
Better Shadows
Better SSAO Quality
Improved Lighting for the entire game
And much more
http://forums.guru3d.com/showthread.php?t=389848