Alan,
As Roel, I'm not a fan of the vignetting either.
I agree with you that the shot is boring. The vignetting seems to improve the image only because it also crops the image down closer around the horses, which are the only interesting elements of the image. This is an example of the need to "fill the frame with the image" (the horses and the immediate area around them - everything else adds nothing to the shot). Either by getting closer, using a longer lens or cropping.
Rich

