I hate Linux Graphics (Linux Hater's Blog)

Another advantage of moving the drivers out of the X server is that it'd be far easier to
completely replace Xorg. Currently if you want to write your own complete windowing system
you'd also have to deal with the very low level stuff of writing a video driver (or porting
one from X), with Gallium3D and friends you'd be able to target a generic API like OpenGL 3
(or another low level API that specializes in this sort of thing) and not have to spend close
to as much time on that hardware-specific stuff.

We probably wouldn't be saying goodbye to Xorg (or X11) anytime soon after Gallium is ready,
but just like Xegl/Xgl and other like-projects, the ideas and gained knowledge could always be
used to imporve Xorg. I'm personally quite excited about what Gallium means for the future of
the Linux desktop, it seems like the current bottleneck is Xorg, with both the Linux kernel
being quite kick ass (wrt non-graphics) and everything above X in dire need of more room to
expand.