When the rut is going strong and a buck has a harem of does, the use of the call in conjunction with a decoy works like a champ. It has been my experience to sneak within 75-80 yards undetected, then give a chuckle with the call and then deploy the decoy. The buck will probably posture then come in if he is going to. Be ready because it will happen fast.
I have also used the call during rifle season ( hunting with a Handgun) to get a bedded buck to stand up. For the record, I think that the ELK call sounds more realistic than the primos one but the lanyard is handy. I also think that a guy can practice calling with just his mouth with similar results.