The original sketch is here, it's absolutely wonderful, and a joy to line and gray, check his stuff out. [link]
This is actually my first shot at doing grayscale. Partway through I feel I lost a lot of the edge and went for streaks on the highlights when originally my shadows had been block shades.
Next time I may go for streaks from the beginning, it will probably look a lot stronger and a lil' more cohesive.