Going back to the original question in this post -- the purpose of the spoiler on the 2003 model. Now that I have the vehicle, and tonight driving home from the airport in a small snowstorm, I got to see the spoiler in action.
It actually has a curve built into it so that it deflects some of the wind down from the top of the vehicle. It's much less obvious than the earlier spoilers, but its smooth curve probably produces a lot less drag.
But, the deflected air did seem to blow much of the moisture off of the back window.
Net - the spoiler seems to have 2 purposes:
(1) to be decorative, although some would debate that,

and
(2) to help keep stuff off of the back window.
By the way, the hydrophilic glass on the 2003 model works, but not nearly as well as Rain-X does. I'm planning to stick with Rain-X on all windows and the sunroof to keep the rain flying off.