Uh, geniuses, thats not a scroll WHEEL, its a scroll BALL. Not a very common feature on mice offered today. I have not tried this Apple mouse, and probably wont anytime soon, but lets get our facts straight here..
I tried a scroll ball mouse once and it really sucked -- not in concept but in quality. I assume Apple did better?
I get the same effect by clicking on the scroll wheel on my Logitech (Cordless) TrackMan Wheel, then using the trackball to scroll around (dunno if Microsoft mice/trackballs offer the same deal; it's been forever since I used one). Also, for those times when precision scrolling (up/down only) is required, the wheel provides a tactile response. Somehow, I don't think Apple can offer the same combination with Mighty Mouse, but if they are, all the more power to them.