the neat thing is that it mimics the api for qtoolbar so you can simply sling actions at it and they show up grouped:
KMultiActionButton* button = new KMultiActionButton(window);
button->addAction( icon1, i18n("Quit"), qApp, SLOT( quit() ));
QAction* action = button->addAction( icon2, "action 2", );
connect(action, SIGNAL(triggered(bool)), this, SLOT(someSlot()));
button->addAction( KStdAction::close( mainWindow, SLOT( close() ), actionCollection() ) );
i still have to implement things like showing menus for actions that have them and respecting action groups (not to mentioned seriously working on the currently crapitudinal eye candy), but i'm interested in feedback from other developers before i spend to much time on it. if you have a Qt4 or KDE4 app (there are currently no KDE dependencies in the class) and would like something like this in your app, please let me know as i'm looking for some guinea pigs, er, test cases before attempting to inflict this upon libkdeui ;)
p.s. no, i'm not trying to replace devel mailing lists with blogs: i've also sent an email off to kde-core-devel, but not all app devels read that.