I learnt to shoot with my father's .22lr Lithgow Model 12 fitted with a rear aperture sight. I have always respected their use as I also find them very fast to use. The longer sight radius helps improve accuracy over other 'open sights'.

AFRO408 has a large diameter one for his .408 custom rifle and a pop up on his BRNO .243 Myra.

I am planing to eventually get one of those NECG rear scope base mounted models. It will be for my FN Mauser 98 .275 Rigby project as a back up in case of a scope failure in the field, but only if I can get positive feedback about them from people who have used one.

I have express sights on my 9.3x62 which post Africa, I would now be confident to use on DG (with a back up). I had express sights installed to keep it 'traditional' even knowing an aperture would be more practical.

Sorry for the rambling reply but I guess for me the choice of 'open' or 'iron' sights comes down to traditional express sights or practical aperture rear sight. Both with the appropriate front bead.