FF = ON is the way to go.
For alot of the veterans this is the only way to go. Simply because it requires more skill and precision, rather than blasting everything and anything that moves.
It also promotes communication and awareness in game. You can't randomly toss nades around for fear of killing a team mate. Your senses become heightened, you start to listen to individual types of gun fire (Bar, STG, KAR, Garand, etc.), footsteps, whether the room is filled with enemies or friendly.
I LOVE IT!! Pure adrenaline!