This is an excellent photograph, hands down. I can tell you put quite a bit of work into getting a nice view of the horse and its companion - if you didn't, it's amazing either way. The fact that the picture is black and white truly adds to the atmosphere of the art. I must say that a couple more shades of black/grey/white might hold the interest of the viewer, but it isn't a big complaint of mine.
The blurred background focuses the eye on the foreground, and it helps the viewer touch upon the peaceful appearance of the picture. Although the multitude of dots do tire my eye a little bit, it's still very pretty. It brings the eye where it needs to be - the tender relationship between a horse and its rider.
You also seem to have paid attention to the rule of thirds, am I correct? The key parts of the photo - the horse's head, the woman's face - seem to be slightly off-center, which makes the picture even more interesting. Overall, I think this is a beautiful image, and I hope my Critique has helped you.