Since I knew I was getting a 24" external display, I very much wanted the smaller MacBook (as opposed to the Pro). I brought a couple of my favorite and familiar photos to the store (on a thumb drive) to load up full-screen to compare both displays. The sales guy was surprised by the side-by-side (as was I). The difference in color and contrast wasn't mild, it was staggering. Those things, and the phenomenon you're describing, had me going with the Pro. (But, man, I'm still extremely envious of the smaller size, and the one pound less weight. If the MacBook had the Air's display, I'd have the MacBook, too.)
How are you liking the macbook and 24" display combination?