It may have become a little complicated by now, because of Qt 4.8 which was recently removed from testing repo. For Qt/KDE apps support you need 'appmenu-qt', for GTK+ apps support you need 'appmenu-gtk' and the 'plasma-widget-menubar' itself of course. You should use 'yaourt' if you want their dependencies to be automatically installed, like this; 'yaourt -S appmenu-qt appmenu-gtk plasma-widget-menubar'. However since there's no Qt 4.8 in repos you have to change 'qt>=4.8' to 'qt-appmenu>=4.7' in appmenu-qt's pkgbuild dependencies line
And KDE's certainly very much productive but sadly underrated.
What do you use for window decoration?
And the emerald theme is a slightly mod of 'gruenstich' by narf41
For Qt/KDE apps support you need 'appmenu-qt', for GTK+ apps support you need 'appmenu-gtk' and the 'plasma-widget-menubar' itself of course. You should use 'yaourt' if you want their dependencies to be automatically installed, like this; 'yaourt -S appmenu-qt appmenu-gtk plasma-widget-menubar'. However since there's no Qt 4.8 in repos you have to change 'qt>=4.8' to 'qt-appmenu>=4.7' in appmenu-qt's pkgbuild dependencies line
That's all