This 'Touch Pad' gizmo, should it be real or a concept in progress, is a very exciting concept for desktop computing.
Sure enough we already have 'tablets' that use pens to navigate the mouse pointer on screen, but the idea of having this Pad-like device only brings in more possibilities with it being wireless and not even needing a pen. We've seen how MultiTouch works with the MacBooks, being able to swipe to switch between programs and many other gestures, but think how the Pad could be customised for a desktop machine
Consider that, just as an example, each corner of the pad could relate to the way the hot-spot 'corners' of the Desktop operate; you touch a corner, and Expose comes up, or Spaces. Apple have never quite hit it with mice - when they do it good, its amazing, but when they do it bad, its dire. Since the 'Mighty Mouse' was so poor, I think they got a lot of stick and the Magic Mouse was a step in the right direction with the touch technology. And its obviously a sign of things to come.
I really think Apple will eradicate Mice all together in the not-too-distant future, and just include a Pad-like device such as this with their iMac, though the option will always be there to connect a mice via Bluetooth. The last revision of the iMac was a dramatic step to making the product even more minimal with just one visible cable, and it wouldn't surprise me if this Pad is a future option. We've just seen how the new Mac Mini has HDMI, and given that Apple have plans for this to be used as a media device with TV's, what better way to control you Mini whilst sitting on the sofa than this device? Its exciting.
The killer attribute for me would be using this with Illustrator/Photoshop. Pen-Tablets are nice, but being able to connect with the surface while drawing could be something special. We'll have to see.
My only concern is just how 'Apple-esque' it is to go from something as small as a mouse to something quite a bit bigger with the Pad; normally, they make things smaller and smaller. Though knowing these guys, they could build the Pad in with the Keyboard, so its all one device... Think about it...