Why do you ask? Are you having problems or are you thinking of purchasing NAV?

You shouldn't really have any problems with Norton Antivirus, you just need to make sure you keep the definitions up to date (as you would do with other Antivirus software).

Sometimes as ive seen, Norton doesnt pick up all viruses.

All the anti virus out there it's all much of a muchness, they do eventually all do the same thing, u really do have to keep it up to date tho, i've used norton and it was good, did the job, now use avg cos it's free! It's unlikely you'll find any problems using it, just make sure your computer is better then the minimum specs and you should be fine