I agree with Desmond in that there's something slightly weird about the Magic TrackPad. Not exactly sure what.
Ah, so it's not just me then. Good good!
I don't know what it is either, but it just doesn't feel quite right to me.
So for now I'm liking having trackpad AND mouse. Only downside is 2 sets of batteries to charge. But it's great having them wireless, as I can pick up either and place them anywhere on the 2 desks (forming an 'L' shape) on which I work.
For me: Mouse on the right, keyboard/trackpad and occasionally wired keyboard in front, graphics tablet and magic track pad on the left. I'm left handed for using a pen/tablet and right handed for the mouse - trackpads can be either left or right equally. It's quite handy having various mousing tools available for either hand, as when one gets tired I can use the other for a while...