I was not impressed with the Supaguard treatment on my paintwork. It is supposed to prevent bird droppings from attacking the paint, failed on this count. Droppings only on there for 2 hours max, had to work hard to remove marks. Paint work on bonnet area very dull after washing until started using Meguairs products.
So IMO not worth it on the paintwork, can't comment on the interior treatment really. But I clean my seats & treat leather regular so they still look like new.