I am getting the same huge performance drop. This is how the game played when it first launched for me as well. Incredibly laggy UI/camera movement with ~15 fps. Then a few days into launch a patch fixed it and everything was crisp and responsive averaging 50~ fps. Now after this recent patch back to the terrible performance. I also did not install the windows update so I know that was not related. Phenom II 955, HD6850.