Depends if you’re talking desktop or server.
On my desktop (well laptop) I run Windows 8, because it’s just easier than Linux for every day computing.
On my servers however, Linux apart from three. Those three are my terminal server, and two PRTG servers.
I use puppet to manage all my configuration because I have so many servers it’s hard to keep track.
As for distribution, Debian runs on most of my Linux servers apart from a few CentOS VMs here and there.
I use Proxmox VE for virtualisation because the combo of OpenVZ and KVM is handy