I have had two Ashley Outdoors Ghost Sights (now XO Sights) on my 45/70 and my Rem700 in 308. Both now wear scopes.
I fould that I could be pretty accurate at the range with it. On game though, I mangaged to shoot 3 deer at 50 yards or so and found none of them. All three were quick shots in the woods and I know I hit them and they died, just not quickly enough. This has never happened to me before or since.
I blamed the front sight, which was a black partidge style post with white center line. When at the range I could take my time and place the small white line where I wanted to on the stationary target. The sight did cover up more of the target than I liked at the range (esp at 100 yards or more). I think on deer the sight was too wide and trying to focus on the top of the white stripe and not the whole sight was difficult. A thinner solid white, black or colored front sight would have been better.
I also was not enamoured of the adjustment arrangement of these sights. Two opposing screws (left and right) for windage. Loosen one and tighten the other, shoot, and repeat. I dropped one screw at the range and it was heck finding it. It seems (IIRC) that I had to unscrew one of the screws in order to adjust the elevation. All of that made it a cumbersome adjustment arrangement. They may have made changes to the adjustment mechanism since I bought mine several years back, but from looking at the pics I've seen, I don't think they have.
My next peep sight will be a Williams or another make/model with some short of click adjustment