Wavedashing is most useful for quickly escaping from close combat with an opponent. Also, it can get you from one end of a stage to the other faster than running or jumping. In some instances, it can also be used as a type of taunt, a means of rubbing your skill in an opponent's face.
Any time you are fighting against an opponent who knows how to do the wavedash, chances are good that that person possesses above-average Smash skills.
Bob:Bitch, you just kept wavedashing.