The overall motion isn't bad, but there's two quite drastic problems:
1. Feet - it seems that they wiggle a bit, like they don't plant firmly on the ground, or the character would move on his heels most of the time.
2. Jumps in the animation - mainly from frame #5 to frame #6. There's very little movement in frame #5 which makes the animation "slow down" for a moment and then there's a sudden jump, like it tries to catch up. You should even out the movement over the course of the frames.
Of course, In case of, for example, attack or running animations, you'll want some frames to have more movement than others to create a more dynamic movement, but a standard (not stylized, not limping etc.) walk cycle should be pretty smooth.
Walk cycle is very regular, so it works best to plan it ahead, for example:
frames#
1. knee bent, foot in the air
2. leg straightening out, feet heel on the ground or towards
3. leg starts to bend, only toes on the ground
4. knee bent, leg lifted (but not as the frist one)
Same movements for the other leg but offset by 2 frames