This app is truly a hidden treasure. Do NOT let the extremely low price fool you...
Once you've watched the demo video on the app maker's website, you will see that this app has amazing painterly effects that you will not find in ANY other paint package (including Photoshop, Fractal Design Painter / Corel Painter, and many other expensive PC-based software packages). With an easy, point-and-click UI, the app lets you choose combinations of cleverly-chosen brush shapes, angles, and color sources (including having your brush color be taken from a photo that you have loaded) that produce literally thousands of different mind-blowing effects which can be tailored to the feeling of each image.
Without a lot of artistic skill, you can get Impressionist/Expressionist-like painterly effects with dots, natural brush strokes, or beautiful calligraphy-like sharp strokes, you can paint with digital blocks or swathes of color on the image to gain a modern effect, or you can apply a huge variety of image processing techniques (including HDR, blur, hue, saturation) either to your image as a whole, to a region of the image, OR simply to the color being used for the brush.
The genuis of this app is how each tool feeds the next in a chain, so by combining effects you can bring out incredible imagery that probably even the app designer has never seen!
Even if you are not interested in painting on your image, the app's unusually good HDR feature, in combination with an easy-to-use crop feature and tools to control image shadows, midtones, and bright areas and the sharpen/blur/hue/saturation settings make this a nice solution for beautifying less-than-stellar photos. There is also an easy feature to add a sharp or blurry rectangular frame around your image to create a nice set-off effect (with either a solid color or the original, unprocessed image in the background).
You can safely ignore the reviewers who whined about the lack of a manual or help screens. On the one hand, this is not a one-trick toy app that one should expect to master in 30 seconds: its chained features are so versatile that they are worth taking time to learn. On the other hand, it's not freaking rocket science either! Watch the video on the website and you'll immediately get a sense of what's possible AND what buttons to push to get that. People who can't even be bothered to watch a few minute demo shouldn't be leaving reviews, or they should confine themselves to the games category in the App Store.
Some reviewers have suggested that they want a "layers" or "text" feature in the app. I think that's kind of like suggesting that one's favorite pencil, ruler, or paintbrush should also be able to make photocopies. I think it's better to think of this app as an extremely versatile tool in an artist's workshop. You can easily export images from this app to Photoshop or other compositing tools to combine with other imagery. I think adding some really heavyweight features like layers would overcomplicate the UI. Just my opinion though.
Definitely buy this app! For just a few bucks you can get unique effects that you won't even see in $800 Photoshop!