I don't understand why they changed Exposé to proportional windows. It's not as easy to find what you're looking for--relative window size was the easiest way (for me) to quickly understand which window is which.
I've always assumed that when they decided to include minimized windows in exposé's results, they felt it was necessary to abandon those properties because it wasn't clear how minimized windows could be fit in with them.
Maybe they tried that internally but it didn't feel natural, or something.