I tried that once on my poor husband. He took a big bite of shepherd's pie (beef, vegetables, mashed potato topping) and promptly horked it back up into his dish.

He got up, found the cookbook, gave me a pen, and demanded that I write in it "do not substitute cauliflower EVER."

The kicker is, some of these things aren't that bad if you don't lie/disguise them.

For example: Roasted soy beans. People tell you they taste like peanuts. That is, in the real world, complete balderdash. However, they can be pretty good (especially with a little cyanne to give them some kick), and I've found if you don't give people the preconcieved reference point, they're more open to it when it's actually in their mouth.