It's still debatable if the lessons learned from touchscreen UIs have any place on the desktop. Touchscreens are a necessary compromise for phones and tablets, somewhat questionable on laptops. But they failed already on the desktop, back in the late 70s and early 80s. Various approaches, including optical sensors, lightpens, etc. were tried, mostly in the CAD industry, pre-PC. They all failed for the simple reason that large motor activity delivers far worse repetitive stress injuries than the tiny motor issues, already enough of a problem with regular users of the mouse and keyboard. Not to mention that even in today's touch-crazed industry, it's still a really stupid idea to be smearing your greasy fingers over your viewing surface if you don't absolutely need to.
I applaud Microsoft for actually thinking about this one, at least a little. They've broken Windows 8 on the desktop in many ways for absolutely no good reason. This is at least a step toward addressing those shortcomings. Apple's doing it better still with their more evolutionary approach, making the existing laptop trackpads work better with multitouch, without breaking much of the previous user experience.
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