Norton will work but it’s such an amazing resource hog compared to other AV programs you almost wonder if they are writing it to be as inefficient as possible.
I use Kaspersky at work and it’s been pretty good so far.
I tried both sides of the fence of going bare for performance and using AV. If you use commercial software and never venture too far beyond websites that are known quantities your chances of getting infected are very minimal. AV will take a toll on performance, often a noticeable one, and if you are a maximum performance hound onboard AV is constant suck on resources.
Having said this if you do a google search that is looking for “naked (insert celeb)” or “cracked copy of (insert popular software)” or any questionable variant thereof you will eventually be infected by trap sites in very short order, and these infections HAVE to caught in browsing mode. If they burrow into your system getting them out is a ferocious slog even for experienced users and may still result in the need to re-format.
If you are a vanilla user with tech savvy you can probably get away without needing AV for a long time. If you have teenagers (or anyone) looking for free cracks and porn, or an older person who will click on anything in their inbox you really, really need effective AV.
My ISP is ATT/Yahoo, and when we first started with them, they had Symantec (Sp?) for download as their supported antivirus. No problems with them. Then ATT switched to McAfee, and it was awful. I have a laptop, and whenever I started it, McAfee would take over, searching for and downloading updates, bogging down my internet connection, and starting a scan, bogging down the CPU. There was no simple way to tell it to pause its scan, no way to tell it to pause looking for updates. I even tried selecting it in the Windows Task Manager to reduce its priority so I could use my computer, but no, I didn’t have permission to do that. McAfee is what led me to find free options.
My wife says it doesn’t cause problems on our desktop, where its always on and it can do its crap in the middle of the night. But for a computer you don’t want on all the time, I’d recommend something else.