Have used PC-cillin for 5 years and has proven excellent. Temporarily used Norton after buying new PC and experienced all sorts of problems, resource hog, excessive time to update on internet (more than my 2 hour ISP limit, then after reconnection Norton didn't remember previous info.). Then on uninstall - it didn't complete successfully, had to rebuild PC.
Used AVG recently and proved excellent, before reverting back to PC-cillin - which has AV, firewall, spyware protection and more...