I have not hunted it, but have been planning a rifle hunt for years now. have a lot of PP's saved up. I was looking into the slim buttes area and the custer NF areas. I have driven through the area and spent countless hours on google earth.
I will say that in my last travels, the deer population seemed to be low, and the locals said as much too. There was a few years of over-harvest and bad winters. I also would suggest the Missouri river area if you can find public land. I have also seen some monster mulies on my travels to Wyoming around the Cheyenne river by wasta. not much public land, but some of the bucks I have seen would be worth the headache to find land. the buck I saw last year easily broke 180 above the Cheyenne river along I-90. it was at night and I almost smacked him with the truck, so it was a quick guestimate, but it was one the biggest mulies I have ever seen alive.
PM me if you would like. I have never done this hunt yet, but feel as if I havce after all the years of planning! The November gun hunt in SD has just never fit in my schedule yet. one of these years it will.