I really like the sillouettes in this shot. The large cactus just off center is a great balance to the sun. I like the striated clouds below the darkness as well.
My only contention with this shot is the amount of dark sky above the features. I think a tighter crop would have given the shot a heavier impact. As it is, I feel as though the large dark swath drags the composition down.
Otherwise, I think it's a fabulous shot that you captured very well.