I've been searching for a way to disable the Unity dash on only 1 of my 3 displays. The 1 display I wish to disable also happens to be the "primary" display. I've found in another forum a discussion as to how enable only the primary monitor to have the unity dash, but I'm interested in only having the dash on monitors 2 and 3.

The discussion concerning primary-only vs all screens configuration is:

"I just found a setting in gconf-editor that will allow you to set the launcher to just your primary desktop: /apps/compiz-1/plugins/unityshell/screen0/options/num_launchers. If you set it to 1, the Unity launcher will only be displayed on the primary desktop. If you set it to 0, the launcher will be available on all desktops."