Good on you, ygf! 
I'm curious, too, about how easy or difficult it was to set up and whether it behaves as described in your earlier link.
the latest ubuntu development version has pretty much everything required in its repository. the hard part was working around bugs/configuration files. Currently I'm using this on my IBM thinkpad t40, with the open source driver, at 1024x768. I start a failsafe terminal from the login screen, and then start up Xgl such that it goes over the whole desktop. (For whatever reason 1400x1050 resolution doesn't work, starting Xgl by itself doesn't work, and some other weird things.)
It does pretty much everything advertised...
- windows are wobbly when moved (and they can stick and stretch to meet the borders of the screen if need be
- minimizing and restoring fades in and out
- it has the Expose feature from mac OS X (one button causes all windows to move around temporarily so they're all fully visible, and touching that button again puts things back to normal)
- it has the alt-tab functionality of windows vista (instead of the window icon in the alt-tab window it shows the miniature display of the window, where it also updates in real time (as in, you can hold down alt-tab and see a progress bar progress in some window))
- it can zoom
- transparency everywhere you want it (somebody recently made a plugin allowing a person to adjust every window's transparency with ctrl-shift-scroll wheel)
- it maps the 4 desktops onto sides of a cube. you can look around the cube arbitrarily, quickly switch to a desktop with the animation of a cube turning, and drag windows to other desktops like that too. Also, windows may span different desktops (cube faces)
- all menus and hover-over boxes wobble briefly while appearing and fade out
some problems currently:
- the driver causes flickering often when using the cube feature
- it's limited to 1024x768 for some weird reason
- window resizes and browser scrolling aren't accelerated, which makes them slow since 2d acceleration doesn't seem to exist either
- the top of the cube can be used for svg slides but i haven't gotten this to work.
- some 2d accelerated things don't seem to work for me (playing movies for instance). I can work around it by playing it on display 0 (the regular X) instead of display 1 (Xgl), since Xgl is just a 3d-accelerated program being run on top of that.
- other 3d programs run inside Xgl don't work. (These can be worked around like the 2d accelerated stuff too)
-sometimes text looks garbled because the screen isn't being refreshed in the right places
it's alpha software so i guess when the drivers and etc improve the average person could made good use with this.
in other news, redhat released a program called aiglx which makes some of the same changes to the x server but with a more incremental approach. both programs share code liberally
Looks pretty cool, but what exactly is the point? 
to make the desktop look better. it's a huge change to the X server, which itself hasn't changed fundamentally since the early days of linux. after Xfree86 forked into Xorg, Xorg underwent a bunch of changes to become a modular X server instead of 16 million lines of code. now that it's modular, people can experiment around with designing better desktops without worrying about how it effects the font server or mouse drivers.
Xgl's major change is that it's an X server that allows indirect 3d acceleration (acceleration to memory instead of directly to the graphics card). Compiz is the window manager that implements the neat features. other window managers (metacity for gnome or whatever for kde) could be altered to include these features by default, and thus linux can compete with windows and mac on the desktop again
