There are no MacOS X viruses. Norton™ Antivirus 11 for Macintosh® removes Windows viruses from your Mac. It can also remove old System 6 thru MacOS 9 viruses. Not one these viruses can infect an Intel-based Mac. By removing them, however, the Mac user cannot act as a carrier of viruses that can infect your Windows-using friends, family, and colleagues. It is up to you to decide whether or not this function is worth your money.
I presume that the suite that you are talking about is Norton™ Internet Security for Mac®. It adds Norton™ Confidential to NAV for a total of $79.99 US. Whether or not you are willing to pay for NAV, at least you know what it does. Norton™ Confidential is not nearly as close a call. The simple exercise of good sense will be more effective than any protection afforded by Norton™ Confidential. If you pay for it, then you have clearly demonstrated that you do not have the sense to protect yourself.