The TrackIR is problematic with fine aiming. Even when you hold your head absolutely still there is some drift which causes your "virtual head" to lose precise alignment with the reflector sight. Usually at the worst possible moment, too, just as you're about to fire.
The fellow in the video was clearly not using TrackIR, but skillfully using the pan views to acquire and track his target. What I've found helpful with TrackIR is assigning two buttons on my joystick just for fine aiming: one key to recenter TrackIR, the second to "pause" it (ie. toggle it "off", pressing this button again toggles TrackIR back "on").
Since I no longer use the hatswitch on my joystick for snapviews, I've reprogrammed it for the different POV's. It sounds cumbersome, but I've found I don't even have to think about it anymore when following a prospective victim. I zoom in, centre and lock TrackIR, fire my guns, zoom out, unlock TRACKIR, and watch my victim crash & burn.
