This might sound like a relatively cosmetic change to proceedings, but the constant restriction of a single magazine and an ever-changing arsenal forces you to stay on your toes, using your fists more than usual and sprinting from gun to gun, your chance of survival changing constantly as you use whatever it is that fate has bestowed upon you to either clear a room or simply try to cut a path to something more powerful. It's a wonderful psychological trick that leaves the player paying more attention to even the most familiar corridors, double-checking every corner for a spare rifle to double back to if things go south.