Is Antivirus Enough?

Recently one of my kids got nuked by the "Personal Antivirus" malware. It's a sneaky thing that is installed when you view the wrong (and that means a compromised site, not a bad site) website and then tries to scare you into buying a $19.95 subscription for updates. The funny part is that this thing installed itself despite Norton Security suite being up to date and running.

Recently Symantec's David Hall made a few comments that raised eyebrows - he said, "antivirus alone is not enough." This is a big revelation coming from a product manager for an antivirus product.

That begs the question, what is enough? I've switched from Windows to Linux on most of our computers, just to get away from having to spend 1-2 days per month fixing Windows. The Linux boxes have their warts, but in general don't crash, get infected, and are much easier to keep updated and working. The only Windows computer in my house is the one my daughter uses for Hoosier Academy classes, and cleaning up Personal Antivirus took about six hours of my time.

Here's the question:
Is antivirus software enough?
Do security suites like Norton help?
Is Windows shot from a security perspective?