I've been using norton for about 7 years (wow that was a while ago). and as long as you keep it upto date it catches everything.
the only problem I've had is that in my last version, the 'live-update' quit working, it would say it ran but the deffinition date would never change so I got about 40 days behind in my deffinitions. after skiping live-update and using the intelegent updater page, a full system scan found a few trojans that my kid had downloaded.
the newest version also checks for spyware on the full system scan(although ad-aware still usually finds one or 2 norton missed).
the live-update, can be set to automatic or you can just manually do it if your good at remembering to (thats how I do it as I don't need to give up any resources to a schedualler). anyway, new deffinitions come out once a week (usually wednesday) and any time a new serious threat is found.
if you skip the live-update and go the inteligent update route. you have to D/L a file and run it manually but those deffinitions are updated almost every day.
btw- I'm fairly sure Chairboy still works for Norton