I have installed the Official 4.2.2 Rom with some S4 Features. It's ok and i do like the improvements made to the settings and icons etc. This is some of the new features.
New enhancements in Android 4.2.2 update
- Android 4.2.2 – Build ID: JDQ39
- New S4 Lockscreen: Multiple Widgets, two Unlock effects (Ripple and Light), improved ripple effect than Android 4.1.2, ability to change clock size and set a personal message
- New Screen modes (From S4): Adapt Display and Professional Photo
- Daydream
- Driving mode
- Actionable notifications
- New Additions in Notification Center
- Completely revamped Settings UI (Tabbed interface – Exactly like the S4)
- Addition of Voice controls (Let’s you control various parts of the phone using voice commands – Galaxy S4 feature)
- Gallery modes have white background (When changing gallery modes to 3D the background changes to white)
- Full screen Samsung apps
- New S-Voice (from S4)
- New smart switch widget
The download link is http://hotfile.com/dl/223736699/03ab0db/I9300XXUFME3_I9300OJKFME1_ILO.zip.html you will need to flash this with Odin. If you have the Original S3 Rom installed then this upgrades and keeps your data! to root again use
http://download.chainfire.eu/229/CF-Root/CF-Auto-Root/CF-Auto-Root-m0-m0xx-gti9300.zip and use odin again to flash this root.