Xubuntu 14.04 Backlit Keyboard not working on Samsung Series 7 NP730U3E with Voria PPA and Samsung-tools installed. Works fine with Ubuntu/Kubuntu 14.04 but prefer XFCE though gather XFCE is likely the issue.
This is a limitation in the version of xfce4-power-manager in Xubuntu 14.04. It was recently fixed upstream (starting with 1.3.0), with updated packages in Xubuntu 14.10 resolving this issue.
xfce4-power-manager is in active development, recent release announcements below.