I used Norton Antivirus for 3 years. Used 2003, 2004 and 2005. Norton Internet Security is good but bad with system resources. Now using AVG Free Edition and Sygate Personal Firewall. I haven't had any problems. Couple of detections healed immediately.
My friends also recommended Karspersky Antivirus. They said they have old AVP team in the company (which was a great team and great AV in 90's), I haven't try it but if you have tried, drop couple of lines, I would like to hear about your experiences.