Very pleasant to look at and even though your DOF has the other bolts blurred they aren't to the point where they are annoying or not interesting to look at. Colors and lighting are right on!
Nice idea to single out one nut. Just a bit more DOF would be nice. That would allow the right face of the nut to be focused as well and still leave the other fuzzy.
Oh I do love shallow DOF and the curve of the subject from foreground to back works so well too. I kind of like that rectangular cross-hatch effect to the right - how did you do that?