For years now experts (and Microsoft) have said that one of the main reasons Windows has proven so popular is the familiarity people have with the OS (aside from other reasons such as flexibility, available software etc.) and we’ve happily accepted this as a reasonable explanation. However, many IT Pros have also said that this is a poor and shallow excuse for foisting on users an interface that is fundamentally inappropriate for them.
Windows 8 conclusively proves it doesn't matter what OS you use!