I am a preservice teacher, but have seen Mystery Science used in a few of my practicums. The school that I was at used Mystery Science as their curriculum, but the teacher who I partnered with would tweak it as needed in order to cover standards and the way that she wanted her students to be engaged. I found that Mystery Science is a good thing to use if you don't have time to come up with your own lesson or if you want something fun for the students. SOME of the lessons are actually really good, and others, not so much. Also, in science, we want our students to pose questions and wonder about what's going on. In Mystery Science, it pretty much tells the students straight up what the problem is and how it should be solved.