Reports of controller lag input in the Killzone 2 demo resulted in detailed research at Guerrilla Games. They have concluded that no changes need to be made.
There were reports of an odd lag to the controls in Killzone 2, displaying a slight delay to shooting after button press (in one report) and reduced accuracy in others.
Being a proud owner of the final game, I did not experience any of these problems. Instead I could appreciate that Killzone 2 featured weightier controls, with a character who moves and reacts more realistically than say Call of Duty.
Moreover, I had no trouble targeting enemies, achieving headshots with relative ease after fully adjusting to the game's control system.
The game's producer Seb Downie has updated the community on the issue.