Another common argument that's along the same lines and, I think, is a more compelling example is "What good is half a heart?" I once saw Richard Dawkins answer this very question, though: small animals (insects, etc.) don't need a heart because just their body movement circulates fluids sufficiently. Then as they got bigger, they developed what is basically an artery with some muscles around it that just add a little bit of a pumping motion to push fluids around. Then as they get bigger, that adaptation continues to gain complexity and centralizes until you have a heart.
I think there's two flaws that people have in thinking about this argument that makes it persuasive. First, "half a heart" is sufficiently close to the concept of "half way along the path to a modern heart" that it seems compatible with their idea of what the theory of evolution posits, but it generates an obviously flawed mental picture (a heart cut in half) that would be absurd to think an animal could survive with. Second, people tend to think about the evolution of individual features in isolation from one another. It's easy to forget that the heart evolved at the same time that body size and metabolic rates were also changing.