Also, here is a list of known issues with 14:
Problem:
https://www.symantec.com/connect/forums/sep-14-bug-renders-windows-7-unable-login
Symantec KB article:
http://www.symantec.com/docs/TECH236543
Problem:
https://www.symantec.com/connect/forums/bsod-after-upgrade-sep-14
Symantec KB article:
http://www.symantec.com/docs/TECH236346
Problem:
https://www.symantec.com/connect/forums/mouse-keyboard-blinking-taking-focus-sep-14-disaster
Symantec KB article:
http://www.symantec.com/docs/TECH236488
I'd test first before upgrading production.