Not sure if anyone noticed this, but after playing a couple games I noticed two flaws in the topic:

1. Movement: You move in the direction of the W key. Literally. Not up though.

I know it's minor, but you can't walk while aiming downward. I've dug numerous holes on Faceoff, Mesa, and other maps, only to get shot before I get into' them, due to (literally) running into the ground. Hopefully there's a fix.

2. Mouselook: Dragging the mouse towards the bottom corners of the screen produces a swerving effect.

I'm not sure if this was intended, but this can sometimes cause a sense of displacement when walking around a tunnel network. You could quickly do a 180 to check your six, and suddenly find yourself falling into a new area, having to either re-route or go with it. Again, something minor, but it bugs me.