For KDE support of a Mac-style menubar has always been rather a hack, both in the past (KDE 3) and currently (KDE 4), see below for some detailed explanations. Best would be to put proper support directly into Qt. Like there is a special handling of the menubar for OS X, there could be one for FLOSS desktops/shells/X.org, given some well-defined standard system.
KDE top menu bar
15/02/2009 by arebentisch