I recently purchased Norton AntiVirus for my new laptop. However, shrotly after purchasing, I read an article from CNET saying that it slowed down system performance by 4%. I am by no stretch of the imagination knowledgable about antivirus software, so I'm asking anyone who's willing to give an opinion--

Is it worth installing Norton AntiVirus?
Is Norton AntiVirus a very good AntiVirus program, or should I consider buying something else?