Version:            (using KDE Devel)
Installed from:    Compiled sources
Compiler:          gcc version 3.2.3 20030422 (Gentoo Linux 1.4 3.2.3-r3, propolice) 
OS:          Linux

This uses the new setCheckedState in KDE libs.

When menubar is visible, text is "Hide Menubar".  When menubar is hidden, text is "Show Menubar".

One liner:
--- konsole.cpp.orig    2004-02-10 01:46:34.252558584 -0500
+++ konsole.cpp 2004-02-10 01:51:01.448938560 -0500
@@ -419,6 +419,7 @@
       {
          showMenubar->plug ( m_rightButton, index );
          m_rightButton->insertSeparator( index+1 );
+         showMenubar->setCheckedState( KGuiItem( "Hide &Menubar", "showmenu", QString::null, QString::null ) );
       }
       index = 2;
       m_rightButton->setItemVisible(POPUP_NEW_SESSION_ID,true);