I used to work at a very busy pub/pizzeria. Customers could order from the standard menu of about 45 items, order a modified standard menu pizza, or they could completely build their own custom pizza. Custom pizzas could be half and half, and have almost any number of sauce, crust, or topping choices. There were at least 75 toppings/sauces to choose from, in addition to the rotating ingredients every two weeks. I can't say that I loved the touch-screen POS system utilized by this restaurant, but the GUI it provided was designed specifically for pizzerias.
I am having trouble imagining how a keyboard-centric interface would require less key strokes than the number of screen-taps for a POS system designed for a pizzeria. For instance, to add or remove a single ingredient to a pizza in the touch-screen POS system it required a single tap. In a keyboard-centric POS system, assuming the ingredients are identified by id starting at 1 through 75, most ingredients would require two keystrokes plus the enter key. My personal experience leads me to believe that specialized touch-screen POS systems certainly work well for some of the more complex restaurant menus.
I am having trouble imagining how a keyboard-centric interface would require less key strokes than the number of screen-taps for a POS system designed for a pizzeria. For instance, to add or remove a single ingredient to a pizza in the touch-screen POS system it required a single tap. In a keyboard-centric POS system, assuming the ingredients are identified by id starting at 1 through 75, most ingredients would require two keystrokes plus the enter key. My personal experience leads me to believe that specialized touch-screen POS systems certainly work well for some of the more complex restaurant menus.