I am using intel i7 920 OC'ed to 3.8. 6 gigs of ram and a NVIDIA 680.
I get 50-60 frames out of cities and around 30-40 in cities. It never drops below 30 though. I have everything set to high, shadows on normal, clouds off (which was a huge FPS boost for me), objects on very low (things in the distance look ugly and there is hardly any grass but it saves frames), and I also have everything disabled on the rendering tab. I also did some ini tweaking from this video right here;
There has been frame drops for me ever since the mod. It is the engine itself but the people getting 5-20 there is something wrong with that picture.