Does the Apple Store let you look at them turned on before you leave the store? I am about to buy one and Dead/Stuck Pixels are my worst nightmare.
stuck pixels are the least of the iMacs screen problems. and no, they won't let you open box after box in the attempts to find the right one (AKA one without screen issues 🙄)... but rest assured, they look great under the lighting of the apple store, most anyway... i wouldn't worry about dead pixels, if i were you i'd be more concerned with bleed out and color casts.