Lemur, you might want to go and have a play with the new MacBooks. The trackpad is in fact, entirely a button.

The tap to click function is not a tap like most pads, but a press. It moves and clicks. You can configure the pad to perform other tasks - for example, the default is that pressing the lower right corner gives a right-click/contextual menu.

There's a whole range of finger gestures that bring real usuability to the trackpad. It's quite a technical feat. I'm one who has always liked an external mouse rather than the trackpad, but I can see myself using one of these on its own.