Has anyone ever seen The Website is Down? In the first episode it looks like the web dude is effortlessly switching between at least 2 different operating systems with a simple alt-tab (I think one was Fedora Linux?), what is he using? Something like VMWare?
Looks to me like VMware Fusion running with Unity enabled. (You can see the little VMware logo on one of the windows.) Unity will display windows from the VM in your native window manager instead of the entire VM in its own window.