Implement “cross-display tiling”, so if you have several displays in extended desktop mode tiling will continue and just shift a window a display further if it hits an edge

Keyboard shortcut: Move active window to display with mouse pointer

Keyboard shortcut: Move all windows to display with mouse pointer

Keyboard shortcut: Alt-tab in preview mode, fullscreen (“Exposé”)

Don't show window shadow on maximised or fullscreen windows (misleading if you have >1 display and the edge of the next display is blurry/dark)