As far as the "need" for a scope, it is definitely on the far side of 200 yards.....farther on a "perfect" shot situation.
My eyes aren't what they once were but I can still consistently hit a squirrel in the head at 25-30 yards (In my younger days I aimed for the eye...not just the head). At 200 yards I still feel confident in shooting deer size game with open sights. At 100 yards any shot is a slam-dunk with open sights.
However, other that when hunting with muzzleloaders or occasionally with the few rifles I have that are not scoped....I "choose" to use scopes because of the aiming precision they make possible. At longer ranges this is very much true but even at how-do-you-do ranges of less than 25 yards the scope allows me to slip the bullet through small openings much easier.
The only exception would be at close range, moving targets. I have tried low-power scopes and peep sights....but on fast moving, close animals I still do better and feel more confident with traditional open sights.
Maybe it is because of the years I spent using those type sights back when we used to hunt deer with dogs....but (for me) scopes and peep sights just aren't as fast to get into action as open sights.
If I "knew" I was going to be presented with a close, fast moving target....such as when following a wounded bear or hog into a thicket...I'd feel most comfortable with a shallow "V" rear sight (express style) and a fairly large bead front sight.
Those situations are admittedly rare. Even when slip hunting (still hunting is what most call it) in thickets....I choose a low-powered scope most of the time. Quick, moving shots "can" happen in this type hunting....but not as often as you might think (that is "if" you have any decent skill at the "slipping" part of the hunt). Most shots will be at standing or slow moving game.....which often aren't even aware they are being hunted.
