Just my 2 cents:
1: The way the background image seems to move up and down when the character jumps is pretty weird and noticable.
2: When moving left or right, it always seems to me like the character just slides around the ground like a puppet being dragged from one place to another. There seems to be no animation for moving left or right, which (for me anyway) sticks out like a sore thumb every time I see it. I know it doesn't have any real affect on the gameplay, but it just bothers me. Either turning or tilting the character in the direction the character is moving would make it look better imo.
3: This is probably just me again, but the way the gun moves when the player is aiming, I always feel like the gun is just stuck to her arm and moves on its own. I don't get the sense that it's the character who is moving and aiming it. It seems to me like they are 2 separate entities, doing their own thing: the character is running and moving, while the gun is aiming. This doesn't affect the gameplay either, but I just can't help but notice it in every dev diary.
I know I might sound like nitpicking, but these are just my honest thoughts.