Rated 5 out of 5 stars

OK. Got it working in Ubuntu 10.10 w/FF 6.0.1. Enter "/usr/bin/dbus-send" (no quotes) for the executable. Then enter "--print-reply --dest=org.gnome.SessionManager /org/gnome/SessionManager org.gnome.SessionManager.RequestShutdown" (no quotes) for the Arguments. This will allow a shutdown without prompting for a password.

This review is for a previous version of the add-on (0.7). 

Rated 3 out of 5 stars

Still cannot get it to work in Ubuntu. After entering this command in terminal: "sudo chmod u+s /sbin/shutdown" which should disable password prompting for the sudo shutdown command Ubuntu still won't shutdown. Any thoughts?

This review is for a previous version of the add-on (0.7). 

"chmod u+s ..." doesn't disable password prompting for sudo. It sets the setuid bit in file permissions. This allows everybody to run the executable with the permissions of the file owner. Usually this isn't an good idea. You have to edit "/etc/sudoers" with visudo to allow specific users to execute "/sbin/shutdown" without an password prompt.

Rated 3 out of 5 stars

Can't get it to shutdown Ubuntu 10.10 w/FF 6.0.1. To use the sudo shutdown command the user's password is required. Anyone get this to work please post here what you did.

This review is for a previous version of the add-on (0.7). 

Have you tried the predefined shutdown command (with ConsoleKit) for Linux?
If it's not working try the following command (maybe ConsoleKit is not present in Maverick):
Executable: /usr/bin/dbus-send
Arguments: --print-reply --dest=org.gnome.SessionManager /org/gnome/SessionManager org.gnome.SessionManager.RequestShutdown
This only works with Gnome.