This is one cool app, and at the low price, a must-have for any iPad artist. The algorithm it uses to fill your strokes and the spaces in-between is a fascinating new paradigm that can surprise you and take you in new stylistic directions that you may not have previously explored.
The user interface is minimalist, which can be nice, if well done. Here, the implementation is awkward: two-finger tap to invoke the small toolbar, but one-finger tap to close. Little user experience nuances like this seem like nothing at first, but all add up to an app that feels like a personal project, rather than a a professional app developers bread-and-butter.
The sketching tools have an unusual interface for controlling pressure and density - kind of neat, but certainly not obvious without reading the help text that the developer provides here on the App Store. The controls are all gestural, pinch to change sample size and twist (like youre rotating something) to change pressure.
The eraser tool is currently broken. Unless you set the density to 100%, you cannot erase to pure white - a faint shadow of the artwork you were erasing remains on the canvas. This makes it very hard to gradually erase something. The smudge feature that was recently added has great potential, and will hopefully become a great tool in future updates.
The sample images that you see here on the App Store are seriously impressive. After a few months with this app I still have not found the control I would need to achieve that subtle level of shading. Regardless, the app has pushed me creatively in many new directions, and is my primary go-to app when I have the desire to sketch but dont have a specific objective in mind. A great creative tool!
I do hope sales go up to encourage the author to sink some real development hours into this app and make it truly live up to its awesome potential!