I have been using Norton all my life with no problems so far, for spy-ware and ad-ware removal I use other free programs.
I have never had any virus problem, and my edition is an old one, not the latest...People is really reluctant to use it, mainly because of space, they argue that Norton is bulky, which is true, but OTOH I have 40Gb hard drive only, and I can assure you that space is not an issue...
Tried Karpeski once and ended formatting my PC, horrible IMO, it got all the machine stocked, and even after removal was still stocked, so format c: was the only solution viable....I'm not saying that all the Karpeski users are wrong of course, but for me was an only one trial error and period, never again....
Also Microsoft is going to release an integrated solution soon, at least that is the rumor, not sure how good or bad it will be....