And I thought I was only here for the Iris eye-candy.
AWESOME, man! My only criticism is the "armpit gap" (not a detail which I feel is necessary, but I won't argue with artistic interpretation). The shading suggests that it is curving outward, as with the rest of X's "fleshy" parts, rather than inward. Further, there's no "depth" to that border of X's armor as there is with the rest of it.
Otherwise, your detailing (both line and color) is exceptional, and as a whole this image rocks!