Official XXUGML2 4.3 Jellybean.
True AOSP style
AROMA Installer 2.70RC1
OTA Updates
Good battery life
Many Kernels Included
Bloatware Remover Option
Essential Apps included, Install optional
Custom Launchers Option
Build.prop Tweaks
Latest SuperSU and su binary
Updated System/Stock apps
AOSP
Google Keyboard
Google Launcher
AOSP/Samsung Messaging Option
Google E-Mail
Google/Samsung Contacts & Phone (in call screen) Option
AOSP/Samsung Browser Option
Google Desk Clock
Google Play Edition 4.4.2 Camera and Gallery option (flash fixed)
Samsung Camera and Gallery option
UltimaROM Themed Apps
Google Play Store Holo
YouTube Holo
Dropbox Holo
Google Mail (GMail) Holo
Google Calendar Holo
Google Play Music Halo
And many more
Mods
Google Quick Settings
Wake Lag Fix
Custom Boot Animations
CRT Animation
Call Recording Option (Samsung only)
Hostname Changing
No SMS receipent limit/MMS conversion
No SMS in Call log (Samsung Only)
Colour changes and transparency options for Statusbar
On-screen Navigation Bar option
Instal
Copy the UltimaROM file to your Galaxy S3's internal SD card.
Turn off your Galaxy S3.
Boot into Recovery Mode by pressing and holding down the Volume Up, Home, and Power buttons.
Make a NANDroid Backup by selecting Backup and Restore. Select Backup.
Select Wipe Data/Factory Reset. Confirm the action on the next screen.
Select Install ZIP from SD card.
Select Choose ZIP from SD card and then select the UltimaROM file.
Follow the on-screen instructions.
Select Reboot System Now.