Trying yet another program, Procreate. It is the most responsive app I've tried to date. However, it is so responsive that it picks up and amplifies every bit of jitter when drawing a line. It will take some getting used to.

So far SketchBook Pro and Procreate are my favorites. ArtStudio was really nice in that you could set line smoothing to weed out the jitter but it was also very slow. With a line that lagged several seconds after the movement.