In the recent years, software applications for medical assistance, including the telerehabilitation, have known a high and continuous presence in the medical field. Guaranteeing the correct use of these applications induces to incorporate a study of usability in the life cycle of any interactive system. This paper synthesizes the results obtained from a study of effectiveness, efficiency, and subjective user satisfaction conducted with ePHoRt. ePHoRt is a web-based platform for home motor rehabilitation; 39 participants tested the platform. We report the empirical results based on the subjective usability perception and self-reported feedback based on the IBM Computer System Usability Questionnaire. The results suggest that ePHoRt is useful, effective, efficient, easy to use, and its interfaces are acceptable. Overall, the participants are satisfied to use the platform. The main findings of this paper show that the user guidance is a critical aspect to ensure a good usability of the tele-rehabilitation platform. INDEX TERMS User centered design, user interfaces, telemedicine, tele-rehabilitation, agile development, user experience, user study.