Adaptive user interfaces (AUI) attempt to change to better suit their users. They typically start in some default state defined by the system designer. A user gradually adapts the interface to himself through a negotiation process undertaken during software usage. My first impulse is to reject this sort of interface for lacking consistency, but let's make a brief listing of the requirements for an adaptive UI in a multi-user system. (The multi-user stipulation is aspirational, but presents some considerations that must be made even in single user systems)
Mainly, my concern with this type of interface is that it doesn't allow for users from one instantiation of the system to use another without recalling to himself the initial set-up for the system. That kind of hiccup may only come up with multi-user systems and public terminals, but I think it would be useful for, say, the military to be able to switch out systems without the users needing to retrain the systems to their particular set of optimizations and preferences. There's also the consideration of establishing a common interface between systems. If each user can change the interface dramatically, there's no hope of standardization. Of course, we can say that each system has its own idioms and should be open to specialization for that system; however, for a class of systems that I'm interested in which may be called "general purpose" there is a great potential for making all uses of the system intuitive with a minimum of training. That is my goal anyway: to accelerate the rate at which we can come upon unfamiliar systems and become adept at manipulating them, removing many of the crude attempts at personalization and real-world analogy that plagued interfaces in the '90s and 2000s when computer use became more widespread.