Priceline.com Quality Guarantee?

I'm searching for a hotel on Priceline.com and I read their "Quality Guarantee" which states, "If the hotel you purchase does not match our promise below, just call us before your check-in date and we'll change or cancel your hotel reservations at no charge." Alright. I'm just curious about how you would know that your hotel is sub-standard before your check-in date? If you get there, check in, get into bed, and there are scorpions in the bed, is it too late to change or cancel your hotel reservation at no charge? Sheesh!