Getting 4.2.2

You need root to install it and SAMMOBILE posted the original file. Make sure it is for your device (I9300). The warranty will be voided as soon as you flash this....
 
as stated above, make sure you have the international version. if you install this on the us variant you will brick your phone. im hoping the devs at xda can use this to make a us version as i doubt the carriers here are in any hurry to put this on our sg3's. they want us to upgrade our phones not our firmware.
 
Also understand this is an internal test version of the software, not a final release version. It is almost guaranteed to have bugs. How serious, and whether they're merely inconvenient or whether they'll clobber you data only time will tell.