If you have a Magic Trackpad and 3-finger window drag enabled, try dragging a window across your screen (given it some velocity) and lift up one finger. The window will slowly glide to a stop rather than abruptly sticking to window.
It feels very natural. I wonder if this is foreshadowing (a.k.a testing) of new interface effects meant to extend the idea of a physical desktop environment. The effect feels right at home to me. Especially given the "natural" scrolling.