Windows at work, Linux at home. I voted Windows but if I weren't working on .NET I wouldn't be running Windows at all. I wouldn't have said that a month ago, I really like what's been done with Ubuntu 12.04. Windows is basically just a Visual Studio host for me. Once I figure out how to get paid to work with node.js Linux will be my primary OS and Windows will just be a virtual machine running VS. Unless I start working on iPhone apps.