it wasn't just that it was full touch screen. palm pilots were full "touch" screen (or stylus) long before. it was that the things on the screen behaved fluidly when you manipulated them, without lag, allowing you to use the interface _while forgetting that there was an interface there in the first place_.

all you have to do to remember what interacting with a device before apple provided a good example is to find a fairly shitty, poorly-specced android device [0] and interact with it and get frustrated at the ever-present-and-yet-inconsistent lag.

[0] tablets are a good place to look, partly because they usually have more pixels to push than phones