I absolutely hate the dark room in spin class. I can't see! Even though my HR monitor has a light, I have to keep pushing a button to make it come on and I often end up pushing the wrong button and then all the functions stop working. My club has the lights on a dimmer and some instructors only dim them a little, others go all the way to darkness.
I don't ride outside in the dark and I don't want to ride in the dark inside, either. It makes me feel claustrophobic.