The side view walking animation is not in sync with it self. Looking at the front view, I notice that the arms in legs are exactly in tune with each other. Right leg back, left arm back, left leg forward, right arm forward. In the side view however, they seem to be on different pendulums of motion, and it throws off the piece.
Also, I like how his legs looked like they ended in nubs, perhaps you should ditch the toe portion you see from the side.
The side views walk seems unnatural in another way- he's not quite facing the side. When he walks, he goes directly side to side, but his angle dictates that he would actually veer to the side a little.
His head jerks to one direction only. I don't think his head should move horizontally at all, in the side view, hes staring straight ahead, not wobbling his head like hes looking for something. But, aside from that, his eyes move towards us, but not away. Try turning your head steadily to one side but not the other. No one ever does that.
I like the front and back views a lot.