Got my Pre Wow yesterday and had the perfect opportunity to use it today.
Received my X5 35i 2 weeks ago and when the dealer waxed it prior to delivery, they had "waxed" the beige (beige interior) sill plate on the driver's side. About 8 inches long of white, dried wax residue on the textured plastic. Not sure how it got there, but it did.
I hit it today with PW and the provided firm toothbrush. A couple of squirts of PW, about 10-15 seconds of brushing, wiped it off with a damp microfiber towel and dried and it's perfect. Worked great.
So far I'm very pleased with the product.