Your link seems to be broken (404). (Update: it works now.)
However, from what you're saying, that sounds like vnc. I have vncserver already installed and working on my machine, and it's also easy to start another real X server on a different console if I want to do a test like this. Does Xvfb have any advantage over these?
Xvfb is not like vnc at all. From the Description section of the man page:
Xvfb is an X server that can run on machines with no display hardware and no physical input devices. It emulates a dumb framebuffer using virtual memory.
The primary use of this server was intended to be server testing. The fb code for any depth can be exercised with this server without the need for real hardware that supports the desired depths. The X community has found many other novel uses for Xvfb, including testing clients against unusual depths and screen configurations, doing batch processing with Xvfb as a background rendering engine, load testing, as an aid to porting the X server to a new platform, and providing an unobtrusive way to run applications that don't really need an X server but insist on having one anyway.
That still sounds quite like vncserver to me. Vncserver is an X server that doesn't display anywhere. You can connect to it with vncviewer or the viewer written in java to view the output and interact from another machine, but it can also run without any viewer attached. (This applies only for X. The Windows vncserver works differently: it just mirrors the real display.)