Version: (using Devel) OS: Linux Installed from: Compiled sources In System Settings -> Appearance -> Style -> Workspace, selecting a theme via the keyboard does not activate the Apply button and permit you to apply the new setting. I have created a patch changing it to use the activated signal instead of the clicked signal. The patch is on reviewboard at: http://reviewboard.kde.org/r/3542/
Patch has been approved for committing, should be fixed in 4.5.