We knew that XAA was on its deathbed as this means of 2D acceleration for X.Org graphics drivers was pretty much useless to modern needs, most drivers now support EXA/UXA/SNA/GLAMOR, and the XAA code was pretty much broken. Only some old graphics processors with their vintage xf86-video-* drivers still rely upon XAA, but that hardware should be killed or reworked to use EXA as was recently done for the ATI Rage 128 driver.
Daniel's patch that kills XAA from the X Server was pulled into xorg/xserver early this morning.
Commit 0c6987df in June 2008 disabled XAA offscreen pixmaps per default, as they were broken, leaving XAA only able to accelerate operations directly on the screen pixmap and nowhere else, eliminating acceleration for basically every modern toolkit, and any composited environment.
So, it hasn't worked for over four years. No-one's even come close to fixing it.