"We are not sure exactly what turning on DX10 does, but we do know it causes a large performance drop on every video card." "In our testing we found absolutely no image quality differences by turning this to "On."" The only benefit was being able to use "On/Antialiasing" for 4X AA, but you need a very fast video card to use that setting. If you have a GeForce 8800 GTX/Ultra level video card you can enjoy that setting. But on the GeForce 8800 GT/GTS and Radeon HD 2900 XT you will have to sacrifice other in-game options or resolutions in order to use 4X AA. It is rather a shame because we noticed that 4X AA does improve the visual quality of this game in a noticeable way."