Not sure if this is the right place for this but here are some things I have noticed.
I believe the aiming widget needs a little more contrast as it disappears completely against certain backgrounds, I just don't fight zombies in melee on white concrete or sand anymore because I'm guessing where I'm aiming and I miss far more than I do on other surfaces. It's not so bad with firearms as the coloured outline is still visible even though the widget is not.
I managed to permanently jam a JS-2000 shotgun, it jammed with no rounds in it. I can rack it as much as I like but it wont clear,