There's only one thing worse than anecdotal evidence, that is no evidence (as in your comment). But, I have many friends who barely know anything about computers and are happy OS X users. In the past, I also installed Linux on family's and friends' machines, but they usually reverted back to Windows in days or weeks. This was caused by everything from incompatibility (OO.org/LibreOffice mangles my PowerPoint presentations), hardware incompatibility, instability (program X crashes), incompleteness (what user-friendly program can I use to edit a movie, like Adobe Premier Elements), installation of software that is not in the distro's repositories and confusion (I want to write an e-mail, but see five different programs).
Of course, some of these issues are not directly related to polish, i.e. as hardware support (since Apple only has to support their own) and the availability of widely used applications (Office, Adobe CS, games, etc.). But, OS X also offers users a simple and polished environment, where they never have to use a terminal to do what they want. Needless to say, they even nailed user-friendliness better with iOS.
Unfortunately, many computer-savvy people are blind to the concerns of the average computer user.