Well, let's make a sharp distinction between response to physical injury and response to mental distress, both usually called "pain," both feeling very similar.

Physical pain serves a definite purpose. It alerts us to injury and trains as a strong negative re-enforcement against getting hurt. Physical pain can of course be exploited in torture to do real, permanent damage, and if given the chance I would vouch to reduce the uncomfortable properties of pain. Physical pain is a damage response (very good) but is too effective (i.e. torture is possible) (slightly bad).

Mental Pain is much harder to pin down, and by my estimates, much worse. A real depression can kill people. Sadness drive people mad, boredom drives them stupid, unmitigated anger drives them to violence, guilt drives them to misery, etc. I say that there isn't anything good about mental pain, or at least the utility reverses rapidly as we go up the scale.

To sum up: Damage response is good except for allowing torture, Mental distress is bad.