This is a wonderful comment by Barbara Wallraff, and describes exactly my feelings about copy-editing (hmm... let me clarify... not about when my prose gets copy-edited by someone else, but when I'm the copy-editor!): the whole interview can be found at identity theory. Here's what Wallraff says: "Really almost the most fun you can have as editor--it's a perverse kind of fun--is turning something upside down and backwards and just buffing and polishing and doing all kinds of stuff to it and then getting it into type--giving the typeset version to the author in a way that he or she doesn't get to see the changes, just the final version. And have them look at it and say, "Oh you did hardly anything." And you are thinking, "Yes. Because I made you say what you meant to say. Clearly, you weren't being detail-oriented about this. Let me do that for you. And now it says what you want.""
I am a truly obsessive copy-editor; more to follow on this.