Personally I'm working on all three platforms and I have reasons (and personal preferences) for each. I want my web servers to run Linux or BSD. I want my mobile computer to run OSX. And I want my work machine to run Windows. In each cases it's a mix of a need for certain applications and a preference for a certain workflow. Sometimes it's even something ridiculous like hating (HATING!) the way mouse acceleration works in OSX....
So, anyway, the way Gabe Newell tries to force an OS-war with his rhetoric is getting on my nerves. Steam is making him shitloads of money. And it'll continue to do so, regardless of Windows 8. And I love that he's opening up the market for Linux, but let's face it, Linux still isn't quite there as an end user desktop system. And unless it is, why should people switch and start purchasing their games on Linux, when they still do their everyday stuff in Win and OSX.