This game has extremely low mouse sensitivity on the highest setting, especially if pointer precision is disabled on Windows, and your mouse is not of high DPI.
You can also decrease MouseAccelDampening, as mouse smoothing makes overall sensitivity slower.
Changing settings in-game reverts these changes and setting the file as read-only breaks the game.
Make this .ini edit after you have configured your key bindings etc.
The game's depth of field effect results in unusually heavy blurring of the graphics. Disabling Post Special Effects will disable the depth of field and make the graphics much crisper, but will also disable tone mapping, bloom, and ambient occlusion.