Okay.
First screenshot is with AO enabled at Quality: http://www.3dart4u.com/images/with_ao.jpg
Second it with AO Disabled: http://www.3dart4u.com/images/without_ao.jpg
No matter where in the world, there is no visible difference.
Before patch 1.5 there was a real, big difference visible, especially with the grass and bushes and so on. Now, it does not make any difference although FPS is effected. With AO enabled (but not visible) it reduces the fps with around 15 to 20 fps.
Forgot to mention: I only use the normal Nvidia configuration screen, no Nvidia Inspector or whatever.