During yesterdays keynote presentation of Android 4.1 Jelly Bean at Google I/O, you will have heard talk of 'Project Butter.' This is the new, 'buttery smooth,' UI coming along with Jelly Bean. To highlight just how good this is, Google Mobile has uploaded a demonstration/promotional video to their YouTube channel.
In the video, you see a vastly slowed down comparison between two different Galaxy Nexus phones. One runs Ice Cream Sandwich, the other is packing Jelly Bean. We won't spoil the ending, but it's pretty impressive.
Source: Google Mobile (YouTube)