Well, I attempted to try it, and considering I haven't done too well the last 2 times I tried King mode, this time I would have conquered the world after like 20 turns if it wasn't for restarting ivs. =P I don't even know how many times I've killed a civilisation..
Let's see.. first was..
Greece,
India,
China (restarted)
France (restarted)
Japan
Then because I was getting bored, I decided I'd stop wiping out other civs and let them live just for a challenge, but I still "monitor" their growth and have had to take a city from America (restarted) and also when I arrived in the Americas I destroyed all known Aztec (restarted) cities but there was one I missed. =P (That was before I started being nice. =P) And Babylon (restarted) has been very nice to me so far, except for the fact hat I discovered their existance when I was about to build a city like 1 tile away. =P