Models and Theories in Human-Computer Interaction/GOMS and Human Nature
GOMS and Humans (Steven Campbell)
People are creatures of habit, it's very true that our smart phones (for example) are very customizable and provide great latitude in the ability to change the makeup and positioning of how to do 'X' task, but people do like at least some of what they have used before. Once they have started using a specific key setup on a phone they are probably going to continue to use it. In this case Fitt's Law dealing with linear tasks where the relationship between the size of the control element and the time to connect with that target.
However given that we are in an era where swiping, gesture based, and other input mechanisms are being made available, a task based analysis via GOMS provides the type of analysis needed as it breaks actions down to a user case style format. Looking at the actions taken from the perspective of what are the goals we need to accomplish, what are the steps to that goals, and is the sequence we perform those actions/step to reach the goal(s).
Although GOMS falls short in the user unpredictability and only assess usability (leaving functionality out of the picture).