On balance, I've had about as many good results from ringing the gong as bad ones. However, the good results include villagers gaining wisdom and becoming younger, whereas with the bad ones, although they sometimes cause a flurry of activity, the effects don't last too long, and can in some cases actually be beneficial.

For instance, a sudden outbreak of sickness can mean you are kept busy healing the villagers, but it helps to advance the doctors' skills. When I've had all my food wiped out I've had to pile all the working villagers, whatever their skill, into the ocean to fish, and drag any that walked out without a catch back in again. Although it meant I was busy for a while, it meant that every villager had at least some training in farming, which made it easier when things later returned to normal.