I should add “on the Mac” to that title, but I’ll avoid any born again references for now. By virtual, I’m referring to the ever so wonderful virtualization, the ability to run a guest OS within another (see wikipedia entry on virtualization for more). For me, on my iMac, I’m using VirtualBox. It’s opensource, from a company which was recently purchased by Sun. My primary use will be quick access to an OS to test configurations or run (windows-only) software. I currently have debian and ubuntu versions, will get a Windows (Vista probably) as soon as I am willing to shell out the $$. Right now, for the few windows-only apps I have, I VNC to my seldom used windows boxes (Vista, Win2k).
VirutalBox has guest edition software for Windows and Linux which adds nice features such as mouse pointer integration and integrated windows. Plus, sharing host directories is very easy. These features are available in the other commercial virtual host solutions I’ve looked at.
OS installation was a breeze for the Linux distributions, as I simply downloaded the iso images and mounted it as cdrom for the guest installer to use.