We can view interface metaphors as tools for accomplishing tasks. An argument about what is the "best" interface model may be like an argument about whether a hammer is a better tool than a saw. It is hard to drive a nail with a saw, and it is difficult to cut wood with a hammer. Novice tools users need to be provide with the appropriate tool for a particular task, and expert tool users need to have a multiplicity of tools and the knowledge to select the right tool for the task.
The results of the experiments described here support the value of a consistent interface metaphor for novices, if the metaphor is appropriate for the task at hand. However, the results also support the value for experts of having multiple interface metaphors available for tackling complex tasks. There are better designed and worse designed interfaces, just as there are better designed and worse designed hammers. But our results imply that there will be no one ideal interface -- instead an expert will be the master of a wide range of interfaces, and will select the one most appropriate for the task at hand. There is no need for gratuitous inconsistency, but on the other hand, we must not let "foolish consistency" be "the hobgoblin of small minds."