My uncle bought a Baikal o/u 12ga/30-06 a couple of years ago and put peep sight on it. The following is an email he sent me last night explaining why he has put a scope on it, which is kind of timely for this thread.
It shot like a house on fire with the William's Fool Proof Receiver Sight on it, but there every time I had a chance with it I could either not find the front sight in the dusk or couldn't clearly see the animal. There was the moose up at Armstrong - all I could see was a shadowy form, who knows with a scope I might have picked out an eye or an ear, something for sure - we were tagged for any moose, and it was a moose, I could tell by the tracks there after, but I just couldn't identify it.
Then there was a buck on Barrie Island two years ago, running, I fired two shots at it and never cut a hair because I never found the front sight, (I should have had buckshot in the shotgun and just shotguned it instead of aiming).
There was a big buck came out over here last year, at least I think it was a buck it stood there but I could not see the horns or #### so I couldn't shoot. A scope would have fixed that! And there was a pair of deer on Barrie Island, couldn't find the front sight.
It is funny how something that works so well on a sunny June day does not work worth a damn in late November in the bush.
Live and learn. Except I have learned that lesson twice now, as my first rifle a 336 Marlin .35 Remington had a Peep sight and the same things all happened.
Maybe I am a slow learner.
Personally I have never been a fan of Peep sights for hunting, but have had great success with good open sights (a flat rear sight with a medium to small v and a fine front sight with gloss white bead). But you will always give up low light shooting opportunities in comparison to a scope with open sights. On the other hand I have missed opportunities using a scope that I wouldn't have with open sights (breathed on it at the wrong moment, got jarred out of alignment, had the power up to high, got snow in it, held it to close to my body on a cold day, etc) most of these things you can handle with experience and more equipment, but sometimes I feel like my nice handy rifle is getting unbearably cumbersome with all the gadgetry.