Context: The usability software quality characteristic aims to improve system user performance. In a previous study, we found evidence of the impact of a set of usability features from the viewpoint of users in terms of efficiency, effectiveness and satisfaction. However, the impact level appears to depend on the usability feature and suggest priorities with respect to their implementation depending on how they promote user performance.Objectives: We use a family of three experiments to increase the precision and generalization of the results in the baseline experiment and provide findings regarding the impact on user performance of the Abort Operation, Progress Feedback and Preferences usability mechanisms.Method: We conduct two replications of the baseline experiment in academic settings. We analyse the data of 366 experimental subjects and apply aggregation (meta-analysis) procedures.Results: We find that the Abort Operation and Preferences usability mechanisms appear to improve system usability a great deal with respect to efficiency, effectiveness and user satisfaction.Conclusions: We find that the family of experiments further corroborates the results of the baseline experiment. Most of the results are statistically significant, and, because of the large number of experimental subjects, the evidence that we gathered in the replications is sufficient to outweigh other experiments.