In fact, since I'm lucky enough to have my own company, I dictate what we use. I have a fulltime freelancer that brought in his PC against my better judgement. After god knows how many headaches and lost funds, I finally convinced him to just buy a damn Mac. Sure enough, he has eventually conceded that he prefers the Mac, but must have his killer home PC for games. How many times have we heard that?! We still have the PC for certain specific things, but I hope even that will end with X (though I guess we'll still need one for testing,etc.).
p.s. I have an ad agency/production company.