Good news T-Mobile USA Galaxy S II users.Samsung have started rolling out the Android 4.1.2 update for your device.
The Jelly Bean update for the predecessor of the S3 will bring several features including changes to the UI
Thanks to SamMobile Blog we have a list of the changes in the update and details about the firmware.
The update will bring the following changes:
Buttery Smooth Performance & Great Stability (Thanks to Project Butter)
Full User Interface Revamp (Same UI as of the Galaxy S III and Galaxy Note II)
TouchWiz Nature UX
Samsung’s S Cloud services
Improved Camera features
New Lockscreen With Many Customization Options
New Features like Direct Call, Smart Stay and Pop-up Play
New Widgets (From Galaxy S III)
2 Home screen modes
New Notification bar With More Notification Toggles
So now you can make your S II look like an S3. Of course it will never get Multi Window officially. But if you have a deodexed ROM, you could use this mod from XDA Developers to get the cool feature.
You can update your (T-Mobile USA) Galaxy S II by using Samsung KIES or the OTA updater.