The real nicety of the display is that Mac OS X knows when you have attached the display to use its integrated devices. That is, when you’ve hooked it all up, it will use the iSight in the display instead of the notebook’s, and it will use the USB audio on the display and disable the output on the notebook. That is, until you plug a set of headphones into the port on the notebook, at which time the display’s speakers will disable and route the audio directly to your ears automatically.

Good design is invisible.  If you notice a design decision, it’s most likely because it got in your way.  Now, I’m not saying I don’t have frustrating moments with my Mac, but it “just works” a lot more often than any other piece of technology I’ve owned, and serves as a constant reminder of what I should strive for in my design.