Norton has improved slightly with their new 360 version, but they still don't justify their price, and still not the lightest products on the market, not mentioning low detection rates...
Not to mention it seems to just interfere with a lot of other apps - I don't know if it's because it's trying to protect too much, or if it's such a resource hog, but I keep finding threads in which people are having issues with Norton 360. You just don't find that much with a lot of the other AVs out there.