Productivity: how long various tasks take to accomplish in a given time;
Learnability: how much training is needed in order to achieve a specified level of proficiency when undertaking a task;
User satisfaction: subjective responses a user has to the system when asked;
Memorability: how robust the learning about the system use is, and how long ability to use it is retained without retraining;
Error rates: accuracy in carrying out the task (this measure is particularly useful in conjunction with the productivity measures set).