This sketch took 30-60 minutes using SketchBook Mobile Express on a Samsung Galaxy Note II (which I've had for less than two days). This was my first successful attempt at drawing on the tablet.
The built-in "S Note" application is not up to the task, and Fresco -- my previous favorite -- pales in comparison to SketchBook. (I think Autodesk has a teeny bit more experience in this area.
Drawing on a tablet this size is a bit challenging because the limited screen real estate makes the UI feel cramped, so they have to make performing tasks as efficient as possible.
Anyway, the scritch-scratch look seems to work for me, and the fine line available in this medium makes it look cleaner than in pencil.