I just installed the new Mandriva 2007 Linux Ditro, mainly because it comes loaded with the mother of all eyecandy features! 3D desktop environment, also reffered to as XGL and Compiz. So far this has been in heavy development, and probably will be for some time to come. Well I wanted to share the love, so I took a short video of my first impresions playing with xgl on Mandriva 2007 and I uploaded it to Google Video, enjoy!
Here's soome of the facts:
From Wikipedia, the free encyclopediaX server architecture designed to take advantage of modern graphics cards via their OpenGL drivers, layered on top of OpenGL via glitz. It supports hardware acceleration of all X, OpenGL and XVideo applications and graphical effects by a compositing window manager such as Compiz or Beryl. The project was started by David Reveman and first released on January 2, 2006
Xgl was originally developed on public mailing lists, but for a long time, until January 2, 2006 most  development of Xgl was done behind closed doors. On that day the source to Xgl was re-opened to the public  , and included in freedesktop.org, along with major restructuring to allow a wider range of supported display drivers. X server backends used by Xgl include Xglx and Xegl. In February 2006 the server gained wide publicity after a public display where the Novell desktop team demonstrated a desktop using Xgl with several visual effects such as translucent windows and a rotating 3D desktop.    The effects had first been implemented in a composite manager called glxcompmgr (not to be confused with xcompmgr), now deprecated because several effects could not be adequately implemented without tighter interaction between the window manager and the composite manager. As a solution David Reveman developed Compiz, the first proper OpenGL compositing window manager for the X Window System as well. Later, on September 2006, the Beryl compositing window manager was released, as an alternative to the original Compiz.
OpenGL does not specify how to initialize a display and manipulate drawing contexts. Instead these operations are handled by an API specific to the native windowing system. So far there are two different backend approaches to solving this initialization problem. Most likely the majority of each backend will contain the same code and the differences will primarily be in the initialization portions of the servers.
Hardware-accelerated OpenGL window and desktop rendering, limited to using OpenGL for texture composition, has been in use in Mac OS X, in a technology called Quartz Extreme, since Mac OS X v10.2. Quartz 2D Extreme is an enhancement of this feature and more directly comparable to Xgl. Like Xgl, Quartz 2D Extreme brings OpenGL acceleration to all 2D drawing operations (not just desktop compositing) and ships with Mac OS X v10.4, but is disabled by default pending a formal declaration of production-readiness. Sun Microsystems' Project Looking Glass  is one of the pioneer hardware-accelerated desktops.Microsoft is in active development of a similar technology based on DirectX, named the DWM, as part of its upcoming operating system Windows Vista
Xgl technology requires good OpenGL performance, along with several unique features of recent 3D cards, and for the most part these can only be accessed using binary-only (proprietary) kernel modules for ATI and NVIDIA cards (technically the drivers use a binary-only component coupled to open source code elsewhere). There are some open source drivers for these cards but they allow 2D only, or allow primitive OpenGL 3D capabilities. Currently this is a deadlock situation because graphics card manufacturers have stated they have no intention to sponsor fully open source drivers. Intel, though, has recently announced that it will open source its drivers , beginning with the Intel 965 Express Chipset. This is a milestone in driver development for Linux.