First off, I'd just show the iMac form factor. Live anywhere near an Apple Store or Apple retailer? The fact that that slim-as-a-monitor (almost) package is the entire computer and that it comes with wireless and Bluetooth (so, aside from the power cord, there would literally be no cords if you get a BT KB and mouse and wireless router) is, in my mind, very powerful. It's small, quiet, powerful, and attractive.
OS X is, of course, simpler and more powerful. It might, though, take time to convince a Windows user that it's easier to use OS X. However, the lack of adware/spyware is a plus. Exposé is a cool touch. Dashboard is actually more useful than I originally gave it credit for. Basically, it's a great, safe OS running in a powerful yet unobtrusive computer.