Looks like a touch of blurring upper right of the flower which is distracting. Nice cleaning of the background - nothing distracting at all. I haven't figured this out yet, but you've obviously mastered it!
Excellent clarity and detail. I think I would have gone with a square crop right about where the top of the shadow is on the stem of the flower. That would leave enough negative space for the flower to stand out as you it does here, as it is there is just too much black for me. A very good shot, I like it.
The large amount of negative space certainly helps to make the centred composition work - good imagination there. I like the incidental, real-world feel of this shot, and the level of detail (especially in the colouring) on the fly. There's something ... kind of casual about the whole thing (in a good way) that I can't quite explain. Speaks of lazy summer days somehow. Must be the light. It's always the light.