I couldn't imagine not running Norton. I once had their window pop up and warn me that a site was attempting to place an icon on my desktop. If you have NAV set for automatic updates, you will get an update the instant there's a new virus definition.
Also, there's a utility within NAV called Guard Dog that will sense a new virus even before Norton is aware of it. Obviously it detects how the virus program is written. You will get a warning and the option to quarantine or delete it.
My neighbor has done a TOTAL destructive system restore at least 4 times in the last year because he won't bother to renew his virus protection. After 4 years of Norton, all 3 of my computers have remained clean, and I've gotten numerous pop ups from Norton of an attached virus in an Email.
I wouldn't be without it.