Just a bit of IRC discussion I thought I'd share. A friend was looking for a way to disable X on an Ubuntu install converted to be a mythtv backend. After a web discussion, another friend suggested passing "text" in on the cmdline. That's a darn good suggestion.
This works in both gdm and lightdm as they both search for this in their startup script (/etc/init.d/gdm and /etc/init/lightdm). Lightdm is the default display manager in Ubuntu 11.10 Oneiric and gdm was the default display manager in prior versions.