....and he is so funny!!! :-D
Any comparison to Quartz right now would be dated. 10.6 has some pretty radical changes coming under the hood.
I have no idea what "all move around together" means, other than that I need to stop posting before the coffee kicks in.
The first thing to realize is that what is fundamental to a complete compiz (or any other compositing manager) is full COMPOSITE extension support for *all* parts of the driver. That is why the application is called compiz, and they are called compositing managers.
When COMPOSITE is enabled, applications are expected to render to an off-screen window surface. The compositing manager can then rendezvous with these offscreen surfaces and combine them in any way that they want.
The *all* parts of the driver includes 2D, 3D an video. 2D is easy, for example, XAA falls back to SW. Xv has some information in the callbacks for the buffer to render to, but then comes 3D. 3D currently renders to where it believes the window _should be_. This means it renders to the pixels on the screen, then compiz renders, then the 3D app renders. When you apply the transforms like the cube and wobbly windows, the app doesn't get new window information until after the transform is complete. The transform itself quite happily renders a blank window (assuming that the contents come from the app).
AIGLX is technically not required for compiz, but for DRI based drivers, it is the simplest path for getting the window contents into an OpenGL texture.
Now with DRI in it's current form, getting this buffer (or redirect buffer as some call it) is very difficult (but not impossible) to achieve.
DRI2 includes sufficient infrastructure to make this possible, an advance memory manager (GEM, TTM, etc) is also needed to allow buffer information to be shared throughout the driver.
(I believe that "Following the Window around" means that GL application is included in the wobbly windows or cube rotation. This is the user-experience - beyond the pixel fighting that occurs between GL and compiz - sometimes called flashing. The redirected direct rendering does push the rendere content into the window. Due to the confusion brought in by redirected direct rendering vs hw accelerated indirect rendering I tend to use the term OpenGL support for COMPOSITE when talking about this.
Ahh yes, that's what I meant :D
another feature that Phoronix could delve into is "resolution independence". Both OS X and Windows have been improving this feature in recent releases. What is the current state of resolution independence in X.org applications?