Coming from Unity, I find a lot of wastage in vertical screen estate in XFCE. One of the biggest offenses is to display the window title, even when the window is maximized. The application icon and its window title is on display in the Panel anyway!
Thankfully, XFCE 4.12 has a solution for this. (Older versions do not have this, sorry.)
Go to Settings -> Window Manager Tweaks -> Accessibility. Enable the option Hide title of window when maximized.
Tried with: XFCE 4.12 and Ubuntu 15.04