I love the AR, wouldn't have over a dozen of them if I didn't. That said, I can't help but opine that people are trying to push this (very flexible) platform into roles it's just not well suited to. With a narrow range of exceptions, big game hunting is one of them. Yes, we have .458 SOCOM and .450 Bushmaster and .50 Beowulf, which are suitable rounds for some larger species at very limited ranges, but here we're talking about severely handicapping magazine capacity and dealing with fairly punishing recoil that is also hard on the rifle. Then we have the various wildcats which don't beat the snot out of the rifle and cut mag capacity by 60-70%, but they're barely adequate for medium game at short range (<200 yards is short range, IMO).
I don't begrudge anyone who wants to use the AR within it's limitations, but I just can't get excited about a proprietary cartridge which is a marginal performer among common deer rifle calibers, and which seems to have been developed for little reason other than trying to reinvigorate a slumped market for one manufacturer. If I actually did want to use an AR-15 for deer hunting, I think the 6.5 Grendel is the best choice.