My Take
I think the videos are short enough to maintain student interest and are content heavy enough to be helpful in teaching. I especially like using this with my students who are visual learners.
How I Use It
I would use Brain Pop Jr. either as a hook to engage students into my lesson or as an accompaniment to my lesson. In the past, I have used it while teaching and paused the video to either explain, expand, or elaborate on what it teaches.