Apple is moving the computer interface in a new direction. Apparently they were not satisfied with one, two, three (lets add some more!) button mice. I can imagine them asking what the value was of having "a little tiny keyboard that you slide around your desk", and subsequently deciding to do something different.
Oddly they've taken the "multiple buttons is confusing" approach and leapt off a cliff. Have you watched a new user try to figure out one of the new apple trackpads? There is so little feedback that they have a hard time even understanding that there is a button available... and its seriously too bad if they meet up with a highly customized desktop supporting multiple gestures. I've noted that even experienced users need to take some time to figure out a peers configuration (concerning which corners do what).... but can you imagine what will happen as the gestures themselves become more and more customizable and as applications add their own gestures to the mix?
This leads to my greatest complaint about the new Magic Mouse -- it doesn't behave the same as a trackpad. In effect having pushed back on movable "mice keyboards" they've also neglected to build a moveable "mice trackpad". Just because it is mounted onto a "mouse" and can be slid around on the desk is no reason, in my book, to introduce a bunch of different gestures and actions. I think they should instead simply mount a full featured trackpad there in mouse form factor. Rather than build their own set of "here is how gestures might be different on this device" instead they should have focused on making gestures customizable in general.
We don't have a mechanism for customizing gestures today and I think there is a lot of software research on making that interface work better .... the hardware needs to be stabilized for a bit longer before that will happen though. I hope to see it soon.
(All this, by the way, leaves your average windows trackpad in the dust; and it is good to see MS is at least experimenting with the ideas. I hope they find the flaws in Apples approach rather than trying to leapfrog in an entirely new direction).