The volume for audio commentary cannot be changed and may be too high for some users. It was lowered slightly in 1.02 to be "more sensible".
On Nvidia cards, if anisotropic filtering is forced through Nvidia Control Panel, "darkness effect" post processing (swirls, blur) is missing. Issue is solved by changing AF in Nvidia Control Panel to application controlled and enabling 16x anisotropic filtering in the game options.
Start the game with the command line parameter -noblur.
Set these parameters to change certain hidden settings or force different options at start-up.