5S- stands for silky, read about the distinguishing feature here!
Silky smooth. All the animations will be synced to 120fps, way more than today's 60Hz limit.
Apple might market this as a retina+ display. Seeing the entire interface at double the refresh rate might make a substantial difference.
IOS7 is heavy on cinematic transitions and physics, which will look amazing at 120Hz.
Scott brought the resolution up to paint photorealistic bit apps. Jony is bringing up the refresh rate to make the UI more real, more nature-like, appearing more responsive.
Obviously this is coming with the new camera, which conveniently captures at 120fps, making slo-mo silky smooth.
They should double the touch sensor sample rate to really make an effect.
Might be made possible by the almost 40% faster 64bit chip.