Puoi mantenere il root usando ad esempio odin mobile pro ma perderai la cwm visto che è un kernel stock
Non esistono al momento kernel custom per questa leacked e sembra che bisognerà aspettare la prima versione ufficiale di JB per averne.........a meno chè umberto non faccia il miracolo
EDIT: mi correggo. E' appena uscita su xda questa guida che spiega come avere il root e la cwm
Easiest way to install the ROM achieve root and CWM recovery:
(make sure your battery is over 50%)
Download the firmware
extract the files and rename the tar.md5 files to .tar (remove the .md5 part)
Download Philz rooted kernel
Download Mobile Odin
copy all the files to your phone
Install mobile odin
open it and let it check for missing files
if u are using the free version u will need to download the flash kernel from chainfire's thread
In Mobile Odin:
go to Open file browse to the folder you copied files in and select the CODE_I9100XXLSJ file
go to Open file again and browse to CSC file do the same for the modem file
Now go to Open file and select Philz kernel
Select wipe data and dalvic cache to avoid running in any errors
this way mobile odin will flash this kernel rather than the stock non rooted kernel
Flash the firmware
your phone will reboot into mobile odin's special recovery and will flash the firmware
the phone will reboot some times just done worry leave it on table
After the phone boots pat your self on the back for doing a good job and thank Samsung for finally providing a good stock firmware since the gingerbread days