It doesn't work then.
I've seen a few occasions where the quality of the meal was remarked upon after this point but a discount was given.
Most recently at Frankie & Bennies in Manchester when my girlfriend's steak was overcooked but she hadn't tried enough to mention it then and, besides, didn't fancy a spit-marinade.
Besides, since you're paying for the goods and service after the fact you are under no legal obligation to pay the price the restaurant ask -- you could even leave your details and go without paying.
(Me, I'm not... in any way intoxicated, Fri 28 May 2010, 17:35, Reply)