The purpose of the mod is to make Max Payne 2 more realistic and tactical, but at the same time to give a dramatic and cinematographic feel to the shootouts.
Here's a quick demonstration video about the Rage Effect.
When you reach the deep bullet time press Reload and you will see Max unleashing his rage. A short and powerfull stream of adrenaline pump in his veins, every shoot is "heavier", the screen flashes and shakes violently, the colors turns to red, the camera zooms in and you have unlimited ammo for the entire duration of the deep bt.
The best description is: "For a few seconds this place was armageddon!"
Also you can see the Blood On Screen feature. When you are hit the screen will become covered by blood, you can understand the how harmful is the shot taken by the texture shape, since it changes accordingly with the calibre of the bullet that hit you.