I updated in the usual way from NIS 2012 to 2013 a day ago, which went generally smoothly. I did have the user interface hang solid when I tried to make some passworded settings shortly after install -- this seemed to sort itself out after several minutes, and to have to do with some kind of unannounced and unrecorded scan the installed update made for itself.
Then today I tried to do a search by using the usual top field in Google Chrome, on release version.
I got a distorted view, which preferred the Ask version of Wikipedia over the real thing, for example. This turned out to be because the search was now being performed by Norton Safe Search!
I could set it back to Google, and did, using Chrome preferences.
However, to have Norton just set this for itself would be very bad -- and with an odor that Symantec is getting kickback from search targets, such as the bogus Ask substitution for Wikipedia.
How about it -- are you seeing NIS 2013 resetting user browser preferences?