Its been a couple of years since I have used mine but they do work. Does seem to be alot more skitish around them but bucks are curious about them. If its that magic rut time decoys can be absolutely deadly on bucks. If they see a doe decoy they truly think they are going to get some lovin. The first nice 8pt I took with my bow was all because of a doe decoy. Long story short with the buck 15 to 20 yards away in some think cover showing off for my decoy I knocked my arrow out of the bow and all the way to the ground. That buck never noticed. I was able to get another arrow in the bow and shoot the buck as it circled out of the thick stuff and came towards the doe. He was never more then 25 yards out as this all happened. If you got a buck decoy out and a buck approaches a couple of things could happen. If the decoys antlers are the same size or smaller then the real buck there is a good chance of your decoy getting attacked. This is because the real deer will do everything it can to intimidate your decoy and of course it wont back down. If the decoys antlers are bigger then the real nuck that buck will still check out the decoy but will show submissive behaviors.
Keep in mind that this is all just in general, with a real deer there is no 100% way of knowing what will happen. A couple of things to do when using a decoy to help fool that old buck. First make sure its set up in a place where the deer can see it easily. When using a doe decoy set it facing directly away from you, a buck will generally circle a doe to scent check her to see if she is in heat. When using a buck set it up so it faces you, a buck will try to approach it head on so it can try to intimidate / challange it. Finally add some movement to it, find some lightweight material that is white and cut it in the shape of a tail. then pin the tail to the decoy and allow the wind to move the tail for you. You can do the same thing for the ears but the tail is usally enough.
Of course this is hard. It's supposed to be hard, thats what makes it great. If it was easy everyone would do it!