Really nice. I might be tempted to rework the area below the lower lip and chin...it sort of looks a bit beard-like in texture to me. A minor point and just my opinion.
It's a small thing, but since the rest of the composition is so strong and the lighting is so dynamic, I think I'd be tempted to lose those lines. Like I said, it's just my opinion...and that's not worth much. It's a really great piece though; a really energetic feel to it...if that makes sense.