The joints in his upper arm look just right - the skin looks airbrushed enough to seem artificial but not so much that the image comes across as shiny and manufactured, just the guy in it does. In any case 'tis a nicely thought out and composed pic, and it's striking because of that. Good stuff!
Thanks for your broad critique (I almost never get critiques likes yours), I always work on experimental stuff so it was my first time to try make the skin look like plastic. But thanks for your comment.