Realism is overrated in my opinion. However, the booster shows very little of what kind of multiplayer the game will have. If the MP is CO-OP based like Left 4 Dead, then I am alright with it. If the MP is Competitive, then it is a terrible booster.
Increased damage. It could...
Allow you to kill people more quickly (with fewer hits).
Leave your opponent more damaged than you'd normally be able to (with the same number of hits), in case someone intercepts you while you're killing him.
Even decide the outcome of a head-on confrontation (with both guys taking turns on damaging eachother, to see who dies first).
For more details about my speculations on the melee, please refer to this thread: