In my experience Klik is exactly right. Most people aren't familiar enough with irons to make good use of them, so would be better off with a low-power scope.
Also, as he hints, the really quick use of iron sights at close range doesn't really involve the sights so much as a rifle that actually fits, very much like a shotgun. I can hit a softball-sized rock every time out to 30 yards without even looking much at the iron sights on my dangerous-game rifles, because the rifles stocks have been modified to fit like a shotguns.
