I work in a school where some of the student/teacher laptops are touch and some not.
I don't need or want touch on a desktop - I've got a full keyboard and and a real mouse.
On my personal macbook pro - touch would be nice, but the mac's touch-pad is pretty sweet, though occasionally I connect a real mouse
On last year's laptop, a 12" windows laptop with a tiny touch-pad - it is crying out for a touch screen.
On this year's model laptops that have windows 8, touch screen and a touch-pad too - it is awesome.
For fast use the touch screen, clicking dialog boxes, installing software, fixing things - you generally don't have to keep typing.
For accurate use the touch-pad. editing, anything that uses both keyboard and mouse.