Classic papers like Jack Carroll's LisaLearning demonstrated that even the best commercially available personal computer was much harder to learn than claimed by Apple. By the late 1980s we had a handle on how to design for the novice user. Much research in the late 1980s and early 1990s concerned experienced user performance. Now it is time to combine the previous efforts and design the interface to be both easily learnable and highly efficient. It is time to accommodate both novice and expert users in one interface.
Experts do more chunking than novices.
This means that they are able to take large amounts of information and see it as connected units. They have a rich set of structures within which to characterize new problems and a sophisticated set of high level concepts about the domain. When using an interface, expert users can quickly form goals and sequences of actions to achieve the goal. They would like the number of interactions to be reduced and thus the action execution is accelerated. They require that the pace of interaction is quick.