I finished the Apprentice level version of this puzzle today. Very nice puzzle, but it pointed up a drawback in pencil solving (at least for me).
I thought I was stuck at one point, and got SudokuSolver to help me with a hint. It turns out that I had completely missed a naked triple (which I am usually quite adept at finding) solely because the puzzle had become so cluttered with my scratched-out pencil marks.
Either I'm going to have to work much more neatly (sometimes a challenge when getting sleepy or puzzle-working in a moving vehicle), or else resign myself to occasionally reprinting a puzzle in its partially-solved state to get rid of the clutter.