Definitely makes a difference
Your review: We coated a brick wall with one coat of this and one coat of the VandlGuard finish coat, and then spray painted black on it to test. With one coat of each type of paint we were able to mostly remove the spray paint with a little "graffiti off" solvent, a scrub brush, and a hose. I think if we add a second coat the effect will be even better.
Pros: Makes it much easier to remove spray paint.
Cons: I heard from the NYC Graffiti Free cleaners that sometimes their power washer will cause this coating to itself peel off. So if you're relying on that program to clean your walls, this may not be the best solution.