While the scenery is beautiful, and the animation really nice, there are some flaws in it.
Look how the left step is so much different from the right step in frame 1 and 13 (two consecutive contact positions):
This is caused by not using hip and shoulder actions in your character. Hips and shoulders rotate along the body axis during the walking action in opposite directions, so that at the contact positions (where both feet are barely touching the floor), both feet are the same distance apart, whatever foot is in front.
In your case, there is no such hip action, so a big step is always followed by a small step. Something similar applies to the shoulders and arm movements.
Then there are the contact positions and what happens in the inbetweens. I've concocted a slowmo version of your animation, with the contact positions and the passing positions (where the legs change positions, the leg in the back becomes the leg in front, and vice versa) marked with an outline of the character (video on YouTube):
This is for demo purposes only. I will delete this video in a few days, unless you ask me to leave it on YouTube
The foot that is on the floor should remain on the floor at the same position, but in your case, it moves. This is what we call "Moho flow". This is often caused by novice animators using a slightly wrong method with bone animation. In all the key frames where a foot is on the floor, the bones that control the leg of that foot should have their selected bone angle key set. In that way, those bones act like they're supposed to act and you don't get any unintentional movement of the standing foot while it's on the floor.
Then there some minor things, but I'll leave it at this.
I hope this helps.
Edit: It seems the video has been pulled from YouTube, or something similar. Here is a version on my .Mac page (it will only there for a few days after this message was posted):
blueman.mov