I moved to this version with the last online update and have so far not experienced any major problems with my PC as such.
However what I have found infuriating is how each year Norton change the software to make it treat the user more and more like an idiot. For example, you used to just right click the icon in your desktop tray to turn off auto-protect, something that is sometimes advisable to do while you install new software as the anti-virus software can sometimes get in the way.
Now you have to find the option to have the tray icon display, and even then when you click it, it pops up yet another menu that asks you how long it should be down for. Do the makers not realise that users are capable of switiching it back on themselves etc.
Another really annoying feature is the Anti-Phising nonsense. This is basically a new gimmick which puts an infuriating bar in your browser which you cannot uninstall. The bar snoops on everything you do and tells you if the website you are on is "safe".
The final issue is with the speed your computer may run at. Norton is a hungry beast when it comes to memmory and processor power. My PC is quite old now, and takes ages to start up.
In future I am going to uninstall Internet Security and simply run just the Anti-Virus, I now plan to use a less demanding firewall like Zone Alarm.
This way, I can live my life how I like and the anti-virus can shut up and just run quietly in the background. As it should.
That said, if you don't know a lot about computers or IT, Norton is probably your best all round bet. Its a shame they don't offer a much more customisable install for more experienced users, who will be annoyed by all the constant warnings and flashing lights.