(https://github.com/HaxeFlixel/flixel/issues/1425): "This is old. The problem is that on iOS 6/7/8/+ there's a very short delay before the Event.Resize is fired, so you're left with the non-retina values for your stage until then. This is why you see so many OpenFL projects do this":
#if ios haxe.Timer.delay(init, 100); // iOS v. > 6 #else init(); #end