First off, the overlapping action you have on the hands (shown most clearly in the profile view of your walk) is very nice, nice and subtle. Wonderful addition.
I think I noticed two things right off the top of my head that could be improved on. The first thing is that your walk is kind of floaty, meaning it doesn't seem to have any weight on it. When someone walks, his hips will seesaw to the sides as the weight is redistributed throughout the walk. Same thing with the shoulders. The hips and the shoulders have opposite angles. If the shoulders are angling down to the right, then the hips would angle down to the left.
The other thing, and maybe this is due to the view of the camera, it doesn't seem as if your character moves his weight over the foot contacting the ground as the other one lifts off to make the new step.
When the walk is in the back view of the character, the arcs on those arms are nice. Too often, I forget to add that arc, so my arms move straight forward and straight back. >.< Those are some nice arcs.
A technical issue is in the feet. If you look at the feet right before they take off from the ground, they double-bounce. I don't know if you did this deliberately or not, but it pulled me out of your animation. Probably an easy graph editor fix.
And I noticed that you put overlapping action in the head also. It's wonderful that you thought ahead to do that, but it seems weightless. When the body goes up, the chin should drag as if it is heavier than the rest of the head (think of the position your head is in when your looking at something in front of you on the floor). In the middle of the step, when the body is at its highest, let the chin "catch up" to the rest of the head (now it weighs the same amount as the head). When the body begins to descend, drag the chin again, only have the head going down first (like when you're looking at something slightly above your head).
Sorry for the long answer. It's 5:30 am, and I can't sleep.

Thought I'd do something productive.
Can't wait to see more of your stuff!
-Chelsey C.