Norman and Nielsen argue that we need to come back to some basic HCI realities in the design of gestural user interfaces. If you look back at the WIMP paradigm that dominates computing today, it came out of the lab almost fully baked. The world of gestural UI, though, is being defined much more in the consumer product space, resulting in a lot more (often interesting) messiness.
“In Apple Mail, to delete an unread item, swipe right across the unopened mail and a dialog appears, allowing you to delete the item. Open the email and the same operation has no result. In the Apple calendar, the operation does not work. How is anyone to know, first, that this magical gesture exists, and second, whether it operates in any particular setting?…Whenever we discus these examples with others, we invariably get two reactions. One is “gee, I didn’t know that.” The other is, “did you know that if you this (followed by some exotic swipe, multi-fingered tap, or prolonged touch) that the following happens?”
Link: Gestural Interfaces: A Step Backwards In Usability (jnd.org)