[Belac]

Actually I think the AI is pretty decent as games go. Much better than the CIV4 AI in that it is willing to attack other AI nations and can master a few basic battlefield strats (even if all that is is artillery+waves of chaff+flanking cavalry, that's something).

My house rules involve massively rich settings and hard research. The time of game when the AI is most challenging is early midgame, when as a player you want to be building forts+mages and racing up the research tree, but instead you have to keep armies around designed to beat waves of chaff. I just give up on reaching the endgame and play like there's nothing above level 6 magic.