When the community college that I work for first started looking at replacing its LMS last year, the faculty professional development team, of which I am a member, needed a way to begin looking into the possible choices to not only give our opinions on the features of the proposed candidates but also to begin learning those features adequately enough to later assist our faculty with their questions. In this regard, the Canvas Free-for-Teachers account provided the best means to learn Canvas and test its features (Canvas subsequently became the LMS of the college.).
The free account allowed each instructional designer to set-up mock courses and add the other designers so that we might experience not just the instructor viewpoint but also the student viewpoint. This greatly enhanced out future ability to advise faculty on not only what to expect on their end of the Canvas interface but also what questions they might find students approaching them with as the students also learned the new LMS. I still use my free account to test features in Canvas from time-to-time. Currently, I have been using the free account to test the Attendance/Roll Call tool as our college is implementing it this spring semester for the first time. I have learned a great deal about how this tool functions and how it appears in the gradebook for both the instructor and the student given the ability to add myself as a student to a test course. At the end of last year, I also used the free account to test and take screenshots of the new UI (which will be implemented at the end of Summer 2016 at our college), so I can give a presentation on it during the adjunct faculty in-service this spring.
In addition, I am also using the free account to look into the possibility of how an LMS might be useful for hosting online courses at my side job (SCUBA instructor).
Overall, the Free-for-Teachers account has proven incredibly useful over the past year.