Current version installs nvidia-settings into /usr/bin. Previous versions installed it into /opt/bin. It works fine in any location. But /etc/X11/xinit/xinitrc.d/95-nvidia-settings and /usr/share/applications/nvidia-drivers-settings.desktop still refer to /opt/bin/nvidia-settings.
Fixed in files/95-nvidia-settings-r1 which is installed by: nvidia-drivers-304.131-r3.ebuild nvidia-drivers-340.96-r4.ebuild nvidia-drivers-346.96-r5.ebuild nvidia-drivers-352.79-r3.ebuild nvidia-drivers-358.16-r4.ebuild nvidia-drivers-361.18-r4.ebuild /usr/share/applications/nvidia-drivers-settings.desktop was already fixed in previous revisions.