I'm running Ubuntu/Gnome right now. One killer feature for me is a particular keybinding I have set up for the 'Windows' key. If I hold it down then I can left-click and drag anywhere on a window and it will move with the mouse. If I hold it and middle-click and drag it resizes the window. And if I hold it and right-click then the title-bar context menu pops up right at the mouse pointer. It eliminates seeking or overshooting the titlebar or corners for window manipulation. I love it.