The aiming is very choppy because it feels like my cursor is "on rails", or stuck in some kind of grid. Not representative of any modern shooting game I've played. I think this would teach the wrong habits if someone were to use it as an aiming coach.

Are you using it on chromium? It's the only browser I get raw mouse events from right now, so other browsers tend to be more choppy.

As for the habits, the point of this program is that it ultimately admits that far domain transfer for aim trainers is difficult regardless of what you do, so it tries to optimize in an absolute sense your motor control over your mouse. That way, regardless of scenario you'll have smoother and more efficient aim.