Car Paint and Interior Leather Protection?

[Rocky]

I closed a deal for a new car, and then the after-sales assistant lady comes round offering paint and interior leather protection. Apparently, this thing once applied, prevents paint from fading and stains from bird droppings etc. Cleaning the car is also easier and cars looks shiny without the need for polish or anything. Questions is, is this a con just to increase the dealers margin or is it really worth it. Can anyone who has bought a car and applied paint protection please let me know what they think. Do it or don't do it and why. Cheers