Unfortunately your other reviewers are shrouded in ignorance so therefore cannot properly criticize this. Fortunately though, I will not allow my personal beliefs to stand in the way of your work.
Starting with your use of color and shading:
You have captured, quite well I must say, the fine shadow and color pigments in the skin, especially in the right forearm and some of the left side of the face.
However, the fingers (excluding the thumb) should be mostly silhouetted, and the thumb should still maintain at least some of the detail that you'd actually find on a thumb. Hold your hand up to a fluorescent light (this closely resembles the color you've used) in a well lit room. You'll notice that despite the natural lighting in the background, the bulb will cause your fingers to be mostly silhouetted and even give them a "reddish" tint.
The face certainly resembles Mr. Jobs but some of the lines for your shading are too heavily weighted, this also applies to the neck.
Where is the lighting from the Apple on his turtle-neck?
The forearm, once again, is fantastic. His overall proportion is mostly correct and you seem to have used foreshortening quite well.
But.. I can't help but wonder if the thumb is in the right place. His eyes just seem far to large, the facial hair reminds me more of a caricature than a portrait and finally, it looks like you rushed his hair.
Overall I'm giving you a seven out of ten because I understand you're not perfect. You aren't going to make this look exactly like Steve Jobs and it's quite obvious you understood that this would be a controversial topic to choose, this shows in the simple title and the almost lack of a description.
However, if you were to revisit this, I would be honored if you took some of the minor errors I noticed into consideration because I do mean well, I'm not just here to troll and bash your hard work. I truly believe that you did a fantastic job on this piece.
I hope to see much more from you on the front page my friend.
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