IR-based "clickers" sux0rs. (Score 1)

At Arizona State we used PRS devices in a biology class of about 200 students. Only one third of the class was allowed to respond at one time in order to avoid overloading the IR receivers mounted on the walls.

For a student, biggest problem was figuring out whether or not the system recorded your answer. Upon a successful transmission, the system displayed a personal confirmation code on the classroom projector. Alas, it could only display around 30 codes before the oldest one was overwritten. With 70 other students in each group frantically submitting and resubmitting their answer, finding your confirmation code on the screen before it got overwritten was a matter of looking at the right place at the right time.

Repeat this two more times for a class of ~200 and the whole thing took 5-10 minutes... for a single question! The teacher eventually decided that the system was too unreliable and slow and used it only for a few bonus-point quizzes so that it wouldn't hurt our grade.