It's a good image with a lot going for it. However, I have to agree with others about the vignette; IMO it's always too much if you notice it right away or not long after looking at the image. The other thing that's been bothering me is the area behind his head. I know the hunched posture is one of the things that depicts his absorption in what he is doing, but I find myself looking at his back and the windows behind it. I would crop a lot of that out - his neck still shows that he is hunched over what he's doing.