It absolutely works. They must be in rut for best results; they must be able hear you grunt; they must not know you are there before you grunt. They must also have had little disturbance. Bucks will be reluctant if quad drivers are cruising up and down nearby trails, etc.
There are more techniques that work, than don't work, so don't stress about your particular situation. Get close to deer without them knowing you are there. Watch the wind. Grunt a few times and listen. Every few minutes, grunt some more and listen.
I sometimes use a grunt to disguise myself when I move. I move as quietly as possible, and very slowly; if I make a noise, I will grunt a few times. I have called bucks to me as I move on trails. Rattling horns works too, but I hate carrying them in the bush.