I believe that the key reason Unix hasn’t taken over the generic office desktop has nothing to do with the technology and everything to do with the people and processes involved.
Thus the generic corporate PC user I talked about yesterday would be completely unaffected if someone snuck in overnight and replaced the PC running Windows/XP below her desk with one running something like Ubantu Linux - as long as our saintly break in artist perpetuated her login ID and password while ensuring that whatever application client she uses first, auto-starts on login.