Nothing is more dissapointing that a flat interface. A good interface will seem to have dimension, even stick out of the page a bit. The key to providing depth is lighting. The Sphere was created by taking a circular selection, rendering light effects, place a fluffy white spot on the upper left corner, and then a slight drop shadow, and adjusting the color.
Light source is very important in creating depth.
Add drop shadows to parts that need to stick up from the panel. You can use drop shadow filters or you can do it manually. See the Drop Shadow tutorial. When you bevel, use filters or do it by hand. See the Beveling by hand tutorial.