You're one up on me. I still haven't quite figured them out yet.
Very good for resizing stuff without any distortion. Select one of the path/shape creating tools (U) (rectangle, rounded rectangle, Elipse, Polygon, etc) Make sure you have paths selected up in the top left, not shape layers. Create your rectangle or whatever, press A to switch to Path Selection Tool, right click path and select add vector mask. Press Shift and F5 to fill with a colour, apply layer effects or whatever. You can resize down nice and easy using the Path Selection Tool and again right clicking on the path (make sure the path thumbnail is selected) and select Free Transform Path.
Couldn't use them on the inner gold layers, they still distorted for some reason, but for the background frame and Carbon pattern layers they were invaluable.