To be honest, I haven't used the multi-touch features (not counting two-fingered right-click). They also could have put a bigger track pad in like the Air, my 17" has a ton of unused space, would have been nice to have more area to drag windows around in and all that.
The multi-touch features just aren't very compelling or integrated very well into the OS. You can use the 3-finger swipe to go back and forth in Safari and then the standard stuff you can do in iPhoto/Preview. But to be honest, doing the motion of expanding your fingers (to zoom) just isn't a very comfortable motion. Neither is the sideways motion (to rotate a picture) when I can just drag my mouse to the appropriate button and click it, or better yet use a keyboard shortcut.
Bottom line is that there is potential but at the moment it just isn't very well used. As time goes by I could see things getting better in terms of integration but even then I think the relatively small size of the trackpad could hold the whole thing back a bit. That's my two cents.