Can we do a poll on which OS hackers use?

All 3, dev on Mac, deploy on Linux, and make sure that your app runs on IE6/7/8 - so there you have all three. Though few months back, I had all threee running in VMWare, my storage was in Linux VM, the app server was in Mac, and the desktop app was in Windows VM. But many times it also depends on what you are developing.

The problem is a lot of us use all three.

ditto. Right tool for the job and all that.

The os doesn't matter as much as the tools : text editor, programming language, etc