Thanks! It was rendered using the always awesome Cycles. The scratches/engravings are like bumpmaps. Cycles calls it "displacement".
About the robot: It looks cool at first glance, but then my eyes are drawn to the
ridiculous looking legs. How is this thing supposed to even walk? Or is it supposed to be a static turret? Either way, the legs are way too small. It looks like the thing will fall over if you sneeze on it. Definitely not what you want for any kind of armed robot. Contrast it with
this.
Other than that, technically the model is very nice. There is nothing that seems to be off with the mesh. Aesthetically, I like the entire middle part a lot. I like the thing going on with the neck. The head I don't like so much. First of all, the head looks pretty boring; it's mostly a few simple shapes. Second, it looks different to the rest of the model: it's flat, while the rest of the robot is round, you know? Third, the beige color reminds me of ugly computer cases from the 90s.
One thing it's missing in general is detail. You made it seem like it's still a work in progress, though. Or you could be going with the flat, featureless design that reminds me of Portal. Here's my advice, anyway: make some lines that split up parts of the model. For example, looking at the arms, it seems like they're just one piece. How were the guns fitted into there? I think you should make it seem like it's made of two pieces. Think about cars, and how you can see the lines that seperate the car from the bumpers and doors. Or look at any plastic object nearby. Small details like that add a lot to a model.