Desktop touch is flawed in one way only, but it's a big one: that no one wants to hold their hands up to the screen for hours on end. It works much better as a table (MS Surface), and perhaps we'll see future computers at 45-degree inclines (you'll notice that Jeff Han demoed multitouch on that kind of system).

"Touch is the future" is a half-truth; the future of computing will probably include a blend of mouse, keyboard, touch, voice, and (hopefully) direct brain interfaces, depending on the task and the use case.