use to use one years ago, but after being noisy and cumbersome, decided it wasnt worth it. not the same as a turkey decoy you can fold up and tuck away in a backpack, so i guess it depends on your area/setup and whether its worth the effect. i could see them being beneficial if you had a place you could stash it instead of having to carry it in/out every day.
Like everything else, they have their place. It is tough to get it all to come together but when it does it is really fun. Let me start with this, make sure it is scent free and easily seen and during a time when bucks are looking for does. Most of all, make sure the decoy is facing the correct way to get the shot you want. Typically they will circle down wind and try to come in from behind, rarely do they come in head first. Take into account the wind and where the decoy is positioned and you will succeed. However the failure I have had were with doe, spooked do will ruin every hunt period. They will either tolerate it or spook the entire field. A good set up also includes the position of the deer coming in so they will not pick you off before they get into the kill zone. Good luck.