The Camera Awesome app is made for the iPhone, but works on the iPad. Some nice features include the horizontal bar (for leveling) and the thirds grid. You can also focus on an object by touching it on the screen - so if there's something in the background you want to focus on, simply touch it. In the photo mode, there are several effects (none in video mode). You can even have slow burst and fast burst (series of snapshots).
You can set it to export to your camera roll as a default. From there, use Wifi Photo
to connect to your computer and select which photos you wish to
transfer (single or in mass).