This has been discussed quite a few times already. Bottom line, no proponent of this idea has ever managed to explain why it would be good at anything, other than Minority Report wish fulfillment.
Touchscreen desktops are a stupid idea, for any number of reasons. There are fundamental ergonomic issues, and just because it's cool and works well on smartphones and tablets doesn't mean it needs to be on our desktops.
Keyboards and mice have stood the test of time, and are by far the most comfortable, productive, and ergonomic choices for the majority of applications.