Well, Nvidia's own GLX is also the cause of some black screen hangs, which are miraculously fixed by replacing them with the X-supplied files.
Actually this is where things get ironic. nVidia replaces the GLX components of the X server whereas ATi does not. Conlusion? ATi has to port their drivers to each and every API/ABI change in the X server's GLX whereas nVidia does not. And yeah, who was it again of the two proprietary driver vendors that delive updates faster...
Well, Nvidia's own GLX is also the cause of some black screen hangs, which are miraculously fixed by replacing them with the X-supplied files.