This app was fantastic for teaching students about volume and surface area, and makes for a great reward to build minecraft-style creations. It can be a little frustrating to change the view, but the center button helps, as does dragging two fingers to move the center point.
Limitations include the number of colors (lots, but it is limited), and there are no textures/background change options. For two bucks though this is a fantastic app and a lot of fun.