I've fitted them on my Cup, cause I got fed up with my exhaust hitting the subframe on the mountain @ Cadwell Park
As already said, you do get more vibrations and more cabin noise to begin with and they to settle down a fair bit, but they will always be harsher than the std items.
If the car gets used on track/gets driven quickly regularly then they do worth it. If it's only a town car with he odd blast down a b-road pobably not.