Obviously W8 is a complete disaster but having a touch screen on a laptop can be nice when implemented correctly. Ergonomically, it makes a lot of sense actually. I compared the strain on my arm when swiping my fingers across the screen of my laptop and when using the mouse. When I rest my elbow in front of the laptop, the strain on my arm is even less then when using a mouse, because when using a mouse I have to retract my arm and can only support the weight of my arm with my hand. When touching my screen, I barely have to move my arm. I move my hand slightly forward and I am able to touch my screen anywhere. Another big bonus is the directness. Using a mouse goes like: looking-for-mouse; move-hand-to-mouse; moving-mouse-pointer-to-correct-screen-location, clicking-mouse-button. With a touch screen I can simply: move arm 10 centimeters forward; press whatever I want on the screen with my finger. It's just more convenient and faster.
But it would be a mistake to use the same UI which was designed for use by a mouse as a touch-screen UI. If a user interacts with the UI using the touch screen, UI elements like menus should be larger and behave differently than when they are accessed with a mouse. For example, scrolling a page could be a swipe on the screen, but using a mouse a swipe would be awkward. Specifically, the mouse paradigm where you move a little pointer on the screen and press a button must not be copied to the touch-screen paradigm, such that pressing a finger on the screen is equivalent for the OS a mouse-button press. Such an implementation would be disastrous. Instead, the UI should adapt to larger fingers, be less picky on where someone lands his fingers, and use larger, dynamically appearing GUI elements so users can see what they are doing, as their hand and fingers are now in front of the screen. And use swipe gestures. Lots.
I think laptops with touch screens are the future, but I suppose it will take some iterations before Microsoft and Apple understand the differences and optimize their GUIs for use by touch screen as input device. In the mean time, creating a single UI for both mouse and touch-screen input is plain dumb and a waste of effort.