I'd say it looks a bit too pixel-y, especially around the line. did you apply a noise filter? If so, I wouldn't. Defects should look done by hand, as if the brush slipped, or something has hit it and damaged it. Of course, how it should look also depends on where you are intending it to go. As in, indoors (spytech, farm, or industrial) or as an exterior texture.
EDIT: one more thing, The dirt should be more obvious and start from the bottom.