Ahh Robot Day...
That was a grand day was it not?
Don't feel too bad, I botched my entry as well. In the overview of this the biggest thing that comes to mind is the Gradients. So..... Many.....Gradients..... Some of them look like you went in by hand and tried to touch them up, but others don't.
One of the biggest flaws with the gradients with this is the conflicting light sources. That alone disrupts the illusion.
It's much better to place a light source and add all reflective material yourself. Although that is very, very time consuming, it's the best bet to have it look good. You should go back and strip out the gradients and just place in reflections in by hand.
Speaking of corrections needed, although at the low resolution it cannot be noticed, but at full size, its painfully obvious. Unclean Line ART!!! Around your lines you can notice thin white lines and halos, that is the result of not making sure that the line art wasn't prepped fully.
Although this is not a full proof route, but usually you can change your line art layer to Multiply settings and just paint under it. Like I said, it works most of the time, but not all the time.
Again in this one you have it running off the page. This isn't working with this piece either. Perhaps with a better background you can really get the feeling of the bot interacting with it's surroundings if he is not running off the canvas.
I think with stepping back and getting some of these minor corrections out of the way could make this a scoutable piece