idbeholdME: To me, it adds to the tension. Knowing that I could run out of ammo at a critical moment or not being able to always use the best weapon I have etc. In Dead Space, difficulty also increases the amount of damage the enemies do so healing items can also be in short supply if you get jumped on/ambushed and have to burn through several at once.
I understand that, the tension. But isn't that the "fear" of - when you die, having to play the same part over again (and over, and over...)?