Honestly... I think the best way to describe trying to hover a heli is like balancing a spinning basketball on the tip of your finger.
-It will stay, GENERALLY centered, but you constantly have to make small movements with your finger to keep it balanced.
-The faster the ball spins, the more stable the b-ball is.... same with headspeed on a heli.
-A bit of wind or breeze will have an effect on it's balance.

One main difference..... if the basketball falls to the ground, it doesn't cost $5-$500 to fix and hours of readjustment for it to work again.