I like the way the sun shines thru the upper part of the flower and not the lower, that bright green leaf in the left part of the photo really takes some of the attetion off of the sunflower, overall a nice shot.
I like the idea of a backlit sunflower, but not sure I like the washed-out look. A bit too hot looking at the top of the picture and lost detail in the center of the flower reduce it's impact for me.