Russ, you're right: su-to-root is in menu in Ubuntu. However, it doesn't seem to be installed by default, and I don't think it's appropriate to cause the whole menu package to be installed on Ubuntu GNOME desktops just because some package need su-to-root. Thus I stand by my earlier conclusion that Ubuntu's lintian should disable the warning about gksu.
Russ, you're right: su-to-root is in menu in Ubuntu. However, it doesn't seem to be installed by default, and I don't think it's appropriate to cause the whole menu package to be installed on Ubuntu GNOME desktops just because some package need su-to-root. Thus I stand by my earlier conclusion that Ubuntu's lintian should disable the warning about gksu.