Today I see an error in SSAO calc, near of the camera you can see fake occlusion. This is definitely wrong. So now is fixed:
I tested different samples, I think 8 it is ok for normal GPU and 4 or 2 for slow GPUs. Is better to be SSAO with 2 or 4 samples than not to be. You can fix that with a blur downsampled x3 for example.
To be or not to be, this is the question :P. In this case, to be, of course!