nice work with this model, Chris. One thing about Prime's head though is that his face plate seems to be a bit too large for his head, almost like it sticks out too much. Something I would do is to select the verts and pull them closer to his face to get rid of the gap. Also, are you using pure sub-D for doing the creases, or are you just adding more polies to the control cage?
Unfortunately the crystal is causing problems when rendering, but here's the casing rendered in MentalRay.