By making the vsync of the screen at a constant 60 frames per second, it makes the UI smooth as, you've guessed it, butter. It even goes as far as to anticipating where your finger is and start drawing from that point to make the UI appear even smoother.
Google showed two Galaxy Nexus smartphones, one running Ice Cream Sandwich and the other Jelly Bean to demonstrate the huge difference that Project Butter makes. It's really quite impressive.
On the demo it worked pretty well by fixing a misheard word (from Known to Though. Accessibility has also been improved adding new gestures and external support for Brail input.
The notification bar has also seen its fair share of changes. It shows you a more prominent looking clock and allows notifications from various apps like Music, Pulse and Gmail to be expanded to give you more details without having to open the app.
When you initiate a search you get a minimalist design card. What’s really cool is when you swipe to the left it shows you a list of Google Search results.
Google Now is another new part of Google Search, which can show you public transport listings, flight information as well as sports results.
Source: CNET/ GSMArena