There are so many things right about this app. The lovely watercolor, miniature sketchbook icon. The marketing site. The “take this everywhere life takes you” video above. And the undo gesture: Place two fingers on the screen and draw a circle counter-clockwise to undo and clockwise to redo. (Though the number of undo/redo steps are limited.)
Download the app for free, and then purchase additional brushes for $1.99 or the entire set for $7.99. But I bet you’ll be really impressed with the calligraphy brush, which comes with the free app. Handwriting and sketching have never looked so good on iPad.