This study investigates operation efficiency and user satisfaction for spatial and temporal shapes of augmented force-feedback fields to be used with computer pointing devices in target acquisition tasks. In an experiment, three different force-field shapes at two different mean force levels were compared, with an electromechanical forcefeedback trackball as control device and with efficiency and user satisfaction as dependent variables. Efficiency was measured by the time required to perform a certain task, and user satisfaction was measured through a subjective rating procedure. Satisfaction results indicate that to a rough approximation, participants can be grouped into those who prefer high and those who prefer low force levels. Members of the former group were most satisfied with force fields with a gradual start and an abrupt ending. This force-field shape also proved to be the most efficient for both groups. When all participants were considered as a single group, none of the effects was found to be statistically significant. A gender effect was also found; in both preference groups women achieved significantly shorter task completion times than men. Actual or potential applications of this research include enabling computer interaction for people prone to repetitive strain injuries and the increment of efficiency and satisfaction in human-computer interaction in general.