I've only tried nukes in one game, huge pangea map, monarch, marathon, as Inca. I owned about half the map, with Germany owning about a third, the rest of the map consisting of 4 small civilizations. Going for conquest, I let loose a huge barrage of nukes on Germany (they actually were no.1 in power). I must of built at least 30 nukes since in 5 of his cities I double, sometimes treble hit due to a very large number of defenders in some of his cities. As Germany had vassals (America and England), this was a huge war, but lasted only about 15 turns! I later won with a diplomatic victory. (Germany had beaten me to the UN by 2 turns - couldn't believe he never went for no nukes, as the first two resolutions went his way). However as fun as it was (and tedious in scheming for a quick result), I won't use nukes again due to the massive destruction on prime land caused by global warming. I lost 2 towns around my capital alone when floodplains turned to desert, and numerous high yield tiles. But I guess for a quickened victory it was worth it.