Depends on the car I personally think. I quite like the lip spoiler on my VS, likewise [although I'd never say it to his face] my brother's VX looks pretty decent with the spoiler it has, even though in general I think VX's look better without one. Of course it can be overdone, and when it does it can easily wreck a car.
One car I think changes completely with a spoiler is the AU Falcon. Put a spoiler on the back and change the grille on the front and it goes from being vomiton wheels to almost a good looking car.