Great design is complicated, and über-detailed. And when it’s done well, most people don’t even notice what went into it. Nothing drives this point home better than the first example in this article, the scroll bar. This article has some ideas for defining the tiny little details (“moments”) of an interaction.
My non-designer friends might find this article insightful as far as understanding just how crazy we designer-types are. Yes, we think about these things in great detail. (Love that diagram of a slightly 3D button viewed from the side!) Yes, it’s very subtle. Yes, it sometimes drives us insane. :)