Some of the Enhancements in the new Jelly Bean Update:

- Buttery Smooth Performance & Great Stability (Thanks to Project Butter)
- New TouchWiz Nature UX (Same UI as of the Galaxy S III and Galaxy Note II)
- Samsung’s Cloud services
- Direct Call, Smart Stay and Pop-up Play Features
- New Widgets From the Galaxy S III
- 2 Home screen modes
- New Notifications bar
- Google Now
This is a PRE-RELEASE version so not official from KIES.
As this is a PRE-RELEASE firmware so expect some minor bugs.
Firmware Details:
Android Version: 4.1.2 – JZO54K (Jelly Bean)
PDA: I9100XXLSJ
CSC: I9100OXXLS1
MODEM: I9100XXLS6
Changelist: 462349
Build Date: 6th November 2012

Download: http://www.techsuplex.com/2012/11/16/android-4-1-2-jelly-bean-rom-leaks-for-samsung-galaxy-s2/