Yes, there does seem to be a litle bit of an excessive corner/edge darkening on this. I dunno...it this day and age of Lightroom, it's so,so easy to apply vignetting. At the time of the application, I often tell myself that the darkening focuses more attention on the central area, but the later I sometimes revise that opinion. I think on this shot, ther entire width of the scene is important, so the edge burn does not help all that much, if at all.
On this shot, the two lighter lines that run down the center of the photo create sections, left, and right, which are interesting in their own right. For me, the darkening hurts my ability to visually explore those two sections. I LIKE the big, stroing oak tree in the center, as the divider, the ruler, of the scene.