At the time, I had a roommate who was a die-hard Windows user. Over several years, I tried to convince him to switch to Mac OS X, with examples like: (a) Just drag/drop a PDF to a printer spool window, and it will print; (b) to install an app, usually you just have to drag it to the Applications folder; to uninstall it, simply drag it to the trash; (c) the simplicity of System Preferences and Software Update; (d) the composited window manager, enabling things like Expose.
What finally converted him was the horrible experience around updating to Windows XP SP3. Recall at the time, Windows Update opened as a control in an Internet Explorer window. Well, he must have waited a very long time until Windows Update no longer supported IE6. So when he attempted to update to SP3, he got an error that the current version of Windows Update required IE7. But for some reason, he could not install IE7 without updating to SP3 -- again, likely because he waited a long time after the SP3 update became available. He told me "I'm never using Windows again" and promptly bought his first MacBook. To my knowledge, he still hasn't gone back.