Small Group Instructional Diagnoses (SGIDs) are informal, mid-semester evaluations of courses, which the instructors request voluntarily. The facilitator of the SGID comes into a class, the instructor leaves, and the facilitator spends about 30 minutes with the students. The first part of the SGID is done in small groups of students. The facilitator asks students to consider two questions, "What are the strengths of this course?" and "What suggestions do you have to improve the course?" After students work in groups for 10 minutes to compose lists of strengths and suggestions, the facilitator calls the class back together as a whole, records the most important strengths and suggestions, and has the class vote on them. These results are then shared privately with the instructor of the course. We collected and analyzed student comments from 45 courses taught by 27 STEM instructors. We found that students value clear lecture and hands-on learning, fair and frequent feedback, flexible and caring instructors, organized classes and resources, and clear alignment between instruction and evaluation. Looking in more detail, we found that students perceived small classes to be more organized than large ones. Students in introductory classes provided the least amount of feedback. Students in introductory classes placed the most value on instructor characteristics such as support and caring about their success, while graduate students placed the least value on instructor characteristics. Finally, female STEM instructors received a disproportionately high number of comments.