Assuming you are referring to the whole string of potential combos with the move itself... Finishing with the third swing is a common choice. Up and Forward options both have a decent knock back, and when spaced well, prove to be a semi-effective KO method and high damage. The Down finish is much more situation, and requires a set-up, as it is a meteor smash. When finishing on the fourth swing, down is the best choice, as it goes into a string of hits, which can pressure those who shielded the combo and missed their grab.
It has a few uses in other areas. Recovery is its primary use. I and others use it occasionally as an aerial stall, so we don't have to jump again to continue combos. It also helps to mess with your opponent, they go to perform a move, and you are hovering just out of reach. You can also use it for edge guard, or even for a low damage mock pivot of sorts. Hope all that helps.