I just installed digikam on my Xfce desktop and found that the tooltips were displayed as very light blue text on a very light yellow background and completely unreadable. I tried switching to a different theme (Settings->Themes->Configuration) and got this error: "Cannot start Colors Settings panel from KDE Control Center." Installing kde-misc/kcmshell makes the control center error go away but then the option just does nothing. I had to install kde-base/systemsettings for all the themes to show up and to get the configuration dialog to work. I still have shitty tooltips by default with GTK+ but at least now I can change them. In the interest of things working out-of-the-box maybe this should be added as a dependency.
Makes sense, added. I'm pretty confident someone else will now complain about unnecessary dependencies though... :P
That's what use-flags are for. On my xfce desktop I don't need KDE windows manager...