Hi Don.. Nice to see the 600 being used for landscape...! Very impressive waterfall and you selected a shutter speed that works well for me too.. I like your composition, for me you have captured all the necessary elements and left out all the distractions..
I like the composition and textures here, Don, but feel it's a bit too "grey" for my tastes.
I would play with dodging the whites of the water and burning the shadows all over a tad more?
Hi Don, very nice capture with the 600mm. Perfect shutter speed for the cascade and I like the arrangement of rock at the bottom too. I would prefer the blacks a touch darker but this a personal preference of mine for B&W.
I as well like the 600 work for landscape. Have to agree with Morkel, this image needs some boosts. I would try the suggestions what Morkel says or would do contrast selective for lights and blacks to bring much more attention to the water.