Late on Friday, December 13, Valve released the first public version of SteamOS. As you would expect, SteamOS is currently very rough around the edges -- it is essentially just a version of Debian 7.1 ...
Before moving to Linux, I mostly just used VirtualBox on Windows to run virtual machines. It's available on Linux too, so I kept using it until I found out QEMU/KVM gives you much better performance.