I guess I am an outlier here in that I have no interest, or more precisely very limited interest, in using a sling to carry a rifle when hunting. I used to carry a 1" leather sling with QD attachments rolled up in a coat pocket with the idea that I'd clip it on and sling my rifle when I had to drag out a deer. I eventually came to the conclusion that I only needed one hand to drag a deer and having the rifle slung over my shoulder or across my back was a bigger PITA than anything. Carrying it in the hand that wasn't dragging the deer provided a sort of balance, as well.
In the northeastern woods where I've done most of my deer hunting on the ground, opportunities often come suddenly and you don't have a lot of time, nor do you want to move around a lot, just raise your rifle with as little commotion as possible and shoot. In a treestand/climber, the last thing I want when I'm 15 to 30 feet up in the air with limited room to maneuver is something hanging off my rifle. I shot one deer walking in to my stand this year and having to unsling my rifle before doing so may have blown that opportunity.
A couple of my rifles are 700's with bolts that don't lock down on safe and the fact that I don't have my rifle slung out of sight, behind my back may be one of the reasons it really doesn't bother me.
I have used a sling on shotguns more than rifles. I have a leather sling with slipknot loops at each end, one sized for the barrel, one to fit around the stock. I'd carry it in a pocket back when we spent most of the winter running fox and coyotes so I could sling my shotgun when I needed both hands free to handle hounds. I also used to use it when manhandling bags of decoys back into the swamps during early duck season.
I've often hunted with a backpack of some sort, but I like to have my rifle in my hands.
