Usability testing should involve more than just "time taken for a new user to become familiar with the interface". Experienced users also need to be observed to

Usability testing should involve more than just "time taken for a new user to become familiar with the interface". Experienced users also need to be observed to ensure that prolonged use also shows desirable usability results. Pop-ups providing first use advice to users may improve usability results for new users. For experienced users, pop-ups are likely to decrease usability. Placing many buttons on a screen will likely make it harder for new users to start using the interface. They will have to investigate many more options amongst the clutter, leading to more decision making ("what is this button? do I click it?") and a corresponding decrease in usability. In the case of GitHub, the question of whether new and/or experienced users regularly need to use the "Edit" button needs to be investigated. The cost of making an interface control highly visible to new users may exceed the cost of experienced users needing to search for help on how to perform the rare action.