I can tell a difference of before and after, but if you didn't know it was there, you couldn't tell a difference. Good mod for the money, but you have to be willing to work for it. The oil pan is a pain to clean up...all that silicone that is left behind was about 30 minutes of buffing and sanding off.
Just remember, after the mod, your ST will hold 6 qts of oil. Remember that if you let someone else change the oil in your car.