I'm sure you are probably a bit disappointed with the score.
This is, of course (as melethia said) a rather difficult scene to expose correctly and I think you have missed the mark a bit. I'm not 100% sure why you would have used ISO 400 for a scene like this, looking at your aperture and shutter speed you could easily have used ISO 200 and still had a fast shutter speed. You could still have used an aperture of around F11 and a shutter speed of 1/200. It would not have made much difference to the depth of field (which is what I believe you were aiming for). Even though the D90 handles noise quite well (same sensor as my D300), I would aim for a lower ISO if possible to minimise unnecessary noise. I know I always get noise in the shadows at ISO 400.
The composition is quite good. I'm interested to know if it was just by chance you came on the scene or if in fact you had been waiting patiently for this to happen.
Overall I think the main thing that lets this image down and keeps it in the mid-4 range is the overall lacking of detail in the image. As others have mentioned it is also lacking sharpness. Was it shot at the longer end of the zoom range? I know with my 18-200 that once I go over 130 mm then the images lack sharpness.
The B&W conversion leaves the image looking a bit flat and I can see some sort of halo along the tree line. It looks like you have selected the sky and darkened it a bit leaving the part closest to the trees a little bit brighter.
Hope you found something to be useful from this critique.
Interesting shot. I think more contrast would have brought out the title/subject a little more and may have even made it a bigger impact to the viewer. Otherwise - the grays don't vary and the photo isn't very dramatic.
I like the idea behind this - nice timing. The conversion looks a bit grainy - a hard shot to expose well since you have the sun versus the dark, shadowed trees.