It's pretty awesome at that moment where you end up stuck under the stage, you know, the part where your opponent starts gloating since you just lost a life. But wait.. you're sonic. Use HA while they taunt, bounce off the bottom of the stage towards the edge (hopefully), use spring. Watch while your opponent craps his pants when you end up next to his taunt charging your forward smash. The last part has only happened once in my life..
Oh yea, if they spot dodge while you do HA, you're pretty much dead. But you were dead anyway, so HA is worth a shot if you end up under the stage w/out a second jump.
Other than that, I use it sparingly when coming out of my spin dash if I miss the opponent but SDJ over their heads. It works well sparingly.
Mostly use it for recovery.