Bit shorter - for stopping the xserver, sudo killall gdm (or xdm, or
kdm, whatever) works with no apparent ill effects. To restart it I just
type sudo gdm (or xdm, or kdm, or whatever).

Another note - if you ever switch which PCI/AGP slot your video card
goes in, you'll probably need to run the command, unless they've fixed
it somewhere along the line.