Very impressive use of DOF! Really makes you focus on the brush and the immediate surrounding brush strokes on the paper.
Two minor things I would have fixed:
1. Small miscellaneous dot on the downstroke on the left.
2. Tighter cropping on the left side to eliminate the gray corner in the lower left.
One thing I may have done differently:
Place the bottle behind the brush or brushstrokes and still apply DOF.
nicely composed, but I don't care for the out of focus inkwell being in the foreground. I think it distracts from the subject. I like shallow DOF, but would tend to place the secondary objects in the back so they do not dominate the image.
The level of sharpening used really upsets the overall feel. The brights stand out too much, especially noticable on the handle of the brush. Nice idea, though. 5