Depends upon the magnitude of the nuclear holocaust, if it was severe the remaining 20% probably wouldn't survive for more than a few years, irradiation would become too globalized.

If the remaining 20% had solid chances of living a long time I wouldn't mind being in the population, it would be interesting to see the directions society went, the change that would happen and the opportunities which arise.

I think it would hurt deep down though, especially knowing just the sheer amount of death, in people, animals and plant life which would have happened across the planet. But I'd still like to give a shot at building a better society for the remaining 20% and avoid repeating history.