Personally I've been a platform whore.
I always owned a PC from win3.1 to XP, but used Macs at school and uni, so I was fine with either.
And while a looked-after PC will normally run fine, I've found Macs to be more hassle-free in the paraoid security department.
About a year ago I was facing the choice for my next system - Vista or Mac. And getting the chance to play with the aluminium intel Mac at work made up my mind, and like many I wouldn't go back to PC now.
I'm aware of my mates boss, who runs a financial-related company blah blah blah, all PCs where they work, and then the man got a Mac for home. Apparently he spent the next day cursing that he couldn't switch to all Macs for work too haha.