I just recently purchased the Madds Buck Growl as well, and I can tell you that its unique grunt sound works awesome. I used it last week to get the attention of a group of does around 60 yards from my stand. I got there attention, in fact I got one to come in to 30 yards and I took her.
I bought it because I seen it in Drurys Outdoors Whitetail Madness video. The results were incredible. You should check it out. It is used to create a dominate buck sound... Best of luck with it