Strong composition and excellent tones; the flare from the sun here helps fill the shadows perfectly. Unfortunately there's a small distracting flare hot spot in the lower left which of course can't be cleaned up in minimal editing. There's also a bit of a sharpening halo along the top edges of the islands in the background.
To me this is a magnificent shot. Quite a piece of art. Now for the critique: Personally I love it and wish I was in an area to take a shot for myself. It meets the challenge as far as I can tell. The Sun Bow is so pretty. The only thing I could say that may have made a difference is the sun is just a tad bit too high and has blown out just a tad more than what I would like to see. This is minimal and beautiful, 10 from me. :)