I like the face but the area where the arms meet the torso dont seem to fit right, maybe ease the ridge out so its smoother as it jumps out as being a bit strange.

Also with all the detialing level that you've put in there, it could do with at touch of detialing where the mech spine meets the back to give it a look of coming out (or going in) the torso as it looks like its just sitting there at the moment with no definition.

Other than that it looks really good.