Excellent image! My only comment is with the lighting. It looks like you used fluorescent lighting, which is fine with me, but the reflection the source casts on the water drop is very visible.
I love the combined effect of the shallow DOF and rich colors combined with this low-key shot. If it were mine, I might have tried bringing the water droplet to thirds, or to a fully centered position-- perhaps even cropping a bit off the bottom of the shot to do so. --8
Excellent shot, good lighting, fits the challenge well, good DOF... need I say more, unfortunately I will...
You could have used the clone tool here to take the small imperfection out of the water droplet, plus the little line next to the reflection in the water. This, to me, would have made this an amazing shot. Due to this I'm afraid I'll have to drop you down a point. Sorry [9]
Beautiful blue hues in the picture. Composition is definitely interesting. The droplet of water has perfect focus. Love the crisp highlight on the droplet.