If you own a Samsung Galaxy S II, you will waiting eagerly for the Android 4.1.2 software update to arrive for your device. However it seems like the update has has already started making unofficial rounds, ahead of its launch. The leaked update shows several new enhancements on top of what you will expect on Android Jelly Bean.The update is based on a test Samsung I9100XXLSJ firmware, but it looks to be stable. It looks like the final version of the update will not be very far from this leaked version.
The update brings the performance improvements you would expect from Project Butter, Google Now along with other features from Jelly Bean. You also get an updated version of TouchWiz with Direct Call, AllShare Play, notification bar enhancements, S-Cloud, Pop Up Play and more.
There is no indication of the availability of the multi-window mode which will be available on the Android 4.1.2 update for the Samsung Galaxy Note II and the Samsung Galaxy S III. Its likely it wont be made available for the Galaxy S II because of its smaller screen size.
source – XDA Developers