Wow... I am amazed.
Have you ever watched Hell's Kitchen? Have you ever noticed how many things get sent back?
I send things back pretty often if it is not what I expected or if I think they underdelivered on the promise. My wife is the absolute pickiest in the world, though.
She likes her food piping hot and will not accept food that is not exactly that. In restaurants she probably sends her food back most of the time, but she just asks them to heat it up. The problem is that you can't just heat food up easily (I have tried to explain this to her many times to no avail), so they end up cooking again, and then she has to sit there for 15 minutes while I eat alone. This has happened to me literally dozens of times.
But when you are paying $25 for an entree, as you will in a nice restaurant, it had better be cooked and delivered perfectly. You aren't paying that money for just the raw ingredients, you are paying for the experience (not to mention the tip you pay).
I also agree with AEROGIRL here that it is completely unfair to think the server will do anything to the food (the cook might, just kidding!) - remember, the waiter is working for YOU, not the restaurant. You tip them and so they want the food to be as good as possible, too.
I was in a nice restaurant here in PHX one night where the entree cost about $35. I got it and the fish & sauce & one side were perfect, but the small portion of loose veggies was undercooked. I just asked the waitress to bring some more well-cooked veggies, saying they were underdone.
But she took my whole plate and came back ten minutes later with everything way overcooked (someone put the whole thing in the fire again). The owner was so mad at her he comped our entire meal (almost $100) and he absolutely would not allow me to tip her. I tried and she said he wouldn't allow it.
But that is the thing about a "foodie" restaurant, it isn't just the food - it is everything about the meal.
I consider cruise ships to be in the same class as these gourmet restaurants, so I will definitely send something back if I am not happy. But to be clear, I am happy most of time, it is not a habit of mine to send food back.
My wife though.. (sometimes it is embarassing, but there is nothing I can do if she is not happy).