I went ahead and upgraded the design of this shield a little bit. It now uses all SMD components (including the PCA8574 chip), has all parts on one side, and uses buttons in place of that tiny joystick thing. Oh, and I dropped the address selection jumpers, since you are not going to have more than one of this on a single dev board anyways.

The pin headers now are staggered for a pressure fit, so that you should be able to put this between your dev board and a display shield without additional headers increasing the height.