I'm using avast, Kerio 4 firewall & Ad aware. It works fine for me and as a non profit home user I can't see the point in paying. I doubt I'd use Norton anyway, it seems to be great if the installation routine runs smoothly, but a complete pig if it doesn't. It also gets the majority of the AV problem postings in this forum.
I agree with Belatucadrus. His expertise is way beyond mine, but I help a lot of friends & colleagues (with help from this forum) and I can confirm that Norton is a MEGA cause of problems. People believe that "it updates automatically"; well, it does provided that option is switched on AND the user is on line regualrly and frequently. But a lot of those I help only go on line briefly, once a week or so, to download emails. Result is they get viruses.
Instead of Live Update of Norton, and because "Palinka" is not a frequent user, "Intellient Updater" should be used if you have not been online for a period. This updater is a complete update when downloaded.
As some of the others have said, NIS2004 can cause a lot of problems and slow down your PC if you're unlucky, but it does get it right for the majority of users. You can give it a go & see how it does for a few days/weeks.