Using Avast Home edition, and I recomended it and install on friends and Family PCs due to the screensaver virus scanning option. Makes it easy to tell someone, just let the screen saver kick on and it'll scan for you. Also the auto update function works great to, albeit a bit scarey when your not expecting it and it announces "VIRUS DATA BASE NOW UPDATED!".
Reasons for not using Norton. Slows otherwise decent PCs down to a crawl, might as well get the virus.
Above every infected computer I've worked on has had some form of Norton installed on it, so whats the point of paying for something that doesn't work anyway. In fact its even worse in the sense that those people do more dangerous things on the internet because they think they are protected by norton.