I took this class as a junior and then later co-taught this class as a senior undergrad in 2015.
The motivation behind the student taught class is that it allows for more classes to be taught than could happen otherwise.
As a student: Like any other class, the quality greatly depends on the work put in by the instructors. I think a student instructor is more likely to care about the quality of teaching, but also more likely to be overworked and not have enough time to dedicate to the course. I didn't think the course was particularly good when I took it due to lack of time from the instructors, but I'm glad the course was offered and that I took it as it got my feet wet with GPU programming.
After taking the course, I did an internship doing GPU programming. Doing this internship, I learned a ton and had a lot of ideas about how to improve the course. This put the idea of teaching the course in my head.
As an instructor: Myself and one other student designed the curriculum, gave the lectures, made the problem sets, did everything. We had a 3rd student who helped with grading. Teaching the course was hugely valuable to me, and also a ton of work. The course was hugely valuable because I learned a ton about GPU programming by teaching it and answering questions. As part of my motivation for teaching was to make the course more how I thought it should be, I didn't reuse many materials from the year before and spent many hours making lecture slides and problem sets. Towards the end of the course, I fell short on time and the lectures and problem sets weren't as good as they could have been. We made the class have a large final project of the student's choosing, and a few awesome things were made. Overall, I'm glad I taught the class, and I think I mostly accomplished what I wanted with improving the learning outcome for students.