My wife used Norton on her computer for a year and had some problems, minor in nature but a nuisance. We recently switched to Panda Titanium Security Suite and she was surprised at how much faster her computer ran. Panda runs a version of Sygate's firewall with a modified GUI.

Prior to Panda, I used Kaspersky 4.5 and the resource hit was just too heavy. Norton? If you're happy with it, and it works for you, great. For us, it just didn't cut it.