HAven't yet been able to order my new iMac. But I went by the Apple Store to see if the Track Pad might be worth trying. I must say I was pleasantly surprised. First, it's not stuck in the front middle of the keyboard as it would be on a laptop. Second, it's much larger than what comes on a laptop. That makes it much better for my size 12 hand! There is a definite clicking movement (too noisy to be able to actually hear anything while in the Store). So, when I get to my order-taker, I'm asking for the Track Pad instead of the Magic Mouse or even the wired mouse!
BTW, Lion makes re-sizing windows much easier, just as I'd read, any side can be 'grabbed' (the cursor changes when over any edge). Nor did I sense any un-natural scrolling behavior; one finger moves the mouse, naturally, and two fingers moves the viewport if there is anything not already visible in the window. So, moving the cursor is just like it is now; move a finger away from you and the cursor moves up the screen and vice versa. Moving the viewport uses two fingers and is completely natural in the sense that one would drag what's visible down to see more of what might be at the top or up to see more of the bottom. It's a perfect analogy of he window showing a piece of what the app has to display; it's a viewport that is often smaller than what can be seen.
Of course, the scroll bars can still be used by moving the cursor over to the right or bottom edge of the window, but I suspect that will become a little used method since the two-finger method will negate placing the cursor in a rather narrow, even if long, target area. Plus, the scroll bar method not only requires moving the cursor but then another click to actually move the viewport. And, if one needs to move diagonally, the two-finger method wins
handsfingertips down!
If you've ever used the 'hand grabber' cursor/tool in PS, yo'll understand immediately...