Originally Posted by acabreram
i will lose the root access with this update??
Yes, flashing any stock Sony ROM will lose your root access, but you can get it back again.
If you have unlocked your bootloader, you can root by flashing a custom kernel like DoomLord's with CWM
(the 757 kernel is the same as the 761 kernel so can use the one for 757) and then reinstall the superuser/superSU zip from CWM recovery. Alternatively, if you want to keep using the stock kernel you can use a "HotBoot" method
Alternatively, you can root with your bootloader still locked by using this tedious and long-winded method: http://forum.xda-developers.com/show....php?t=2688933
(only way to backup TA keys)
PS: if you are a n00b and don't want to lose all your data then remember to uncheck "wipe data" in FlashTool.