I got tasered a few times for training in Corrections CERT. The worst part was the anticipation as I was going to get shot in the back....and they often liked to take their time. It hurt but goes away immediately. Goes away before your mind can really comprehend the actual pain. Losing control of everything was the worst part...IMO, looks more painful when you see it done to others. Pretty damn effective though.
The OC can be bad, and different people react to it in different ways. Also depends on the concentration. I knew of at least one inmate in which the shit would have absolutely no effect on at all. I've seen reactions ranging from having no effect to the person screaming in agony and running into a parked car(lol). When I was first sprayed, the worst part was washing the stuff out of my eyes...the shock of the cold water makes it feel as if you are drowning and you cannot breathe.