Everything has been leaked from the Samsung Galaxy S3 and now people starting porting the apps and launcher on other Android devices. Unfortunately it only works on Samsung based ROMs for the moment, so you cannot flash it on AOSP, AOKP or CM9, though developers are currently working on it and soon you will be able to install it on virtually any Android device.
We’ve tried it on a Samsung Galaxy S2 and it works flawlessly, without any bugs. The Touchwiz 4 launcher is also very fast and can be flashed on your device pretty easy, but you need root access and ClockworkMod recovery running on it.
Remember that before you flash anything you should backup your device, but this can also be done pretty easy using this apps and methods: AppBack to backup and restore applications | SMS backup & restore | Call Logs backup & restore.
First head on to XDA Developers and download the latest TouchWiz UI launcher. Copy the file to your device and then turn it off. Now boot your device in recovery mode by pressing home key + volume up + power buttons simultaneously.
Now go to Install zip from sd card > choose zip from sd card > select the TouchWiz file > Yes. Wait until it finishes flashing the launcher, then reboot your device.
Once your device boots, you can switch to the Galaxy S3 TouchWiz 4 launcher and enjoy it.