For me, the question is not "What OS do you use?" but "How do you collaborate with others?"
The former leads to the predictable slate of arguments we can recite in our sleep. The latter is best done when the code is freely available to all. My personal journey in the last nine months from using to Windows and Linux, to just Linux, all the while being able to do all the work necessary for my job, was enabled by several business apps that have been ported to different platforms. Broad use of open source apps like Firefox, WordPress, Python, PHP, and Komodo were key. OpenOffice, too, works across platforms as well, and it helps that ODF is widely used in the cloud. Like many today, I spend most of my day working with information and services through a browser. For my personal email, I use Gmail, an example of cloud computing.
When I move from “desktop” to “desktop” the most important thing is how I can access my information. If I can access my email and documents for work, and my music for fun, I’m happy. People have or want devices like the iPhone so that they can get work done anywhere, even if they can’t connect their laptops to wifi. Their use will continue to rise.
Linux finally stopped copying Windows circa 2001 this summer with the release of the KDE 4.1 desktop environment. It would be even better if everyone looked at what Apple is doing with usability and design and emulated their continuous success there. Heck, open source need look no further than WordPress, which has attracted excellent graphic designers to build themes and skins. I understand that to gain acceptance for new software, it is easier for users if you mirror the behavior of old software, but at some time you need to step out and innovate in the user interface. KDE 4.1 was a great step forward (for Linux) in this respect, as Vista was for Windows.
Innovation shouldn't merely be driven by maximum "cosmetic" UI consistency. The system -- whether its OS be Windows, Linux, or OS X -- should be held together by well-engineered common design principles and APIs rather than aging string, frivolous patents, and bubble gum (patch) coding.