Here’s an interesting quote by Bill Gates, from a recent interview, in which he describes how he’s never fully satisfied with Microsoft products:
There are always the features that I wanted to get in, or the things that I wish were a little more polished. The people who are good in these companies are really sort of ridiculously demanding people. They have to sort of know when to back off so that thing can eventually ship.
I think it applies to game designers as well: you need to be a perfectionist, but know when to let things go and get the game on store shelves.