I have this to say: wow!
What an experience. Now, surfing the net and doing things on the Mac are just about swiping, pinching - all natural gestures - like how you would use an iPad.
I love the Magic Trackpad and would recommend it to anyone!
It's really magical!
Edit: let me elaborate why I think this is such a great device that, to me, totally replaced the need of a mouse; yes, you don't need a mouse anymore. It is that good!
When I browse a website using Safari, I could just two-finger push up and down to scroll up and down a page. Scrolling was smooth, much like in iPad. I could just swipe left to go back to the page before and Safari actually animates the page being swiped out - if you use Twitter for iPad, you will know what I mean. Swipe right to emulate 'forward' button. (somehow, Chrome for Mac supports the same gesture but it wasn't as smooth as Safari, so Safari is the preferred browser at the moment).
4-finger swipe to launch mission control, so I could easily see all the available apps. Similarly, 4-finger swipe will move between virtual desktops. Very useful when I use Desktop 1 for mails, twitters, RSS news, facebook, etc and Desktop 2 to read PDF manuals and Desktop 3 for Xcode 4.
3 finger tap to click and hold a window so I can resize and move them about. 2 finger tab to emulate right click (or Ctrl-Click)
These gestures are applicable in iPhotos, iTunes, Sparrow, Caffeinated, you name it.
Watch this video and be prepared to be blown away!