There is a pretty obscure feature in current and recent versions of iOS that I think is cooler: some brushed-metal appearing buttons, for example the one that appears to control the volume when you double-click the lock screen to bring up the music controller, subtly change their appearance as you tilt the phone, as if they are actually reflecting light. It probably remains subliminal for most users. I frankly find the parallax effect from the GIF in the linked article a little cheesy; it reminds me, strongly, of those cheap "3D" photographs with the plastic ridges on the surface.