The AI
Just some issues I've noticed with the AI (I posted this in a reply on another forum, but I thought it might get lost in all the other posts):
It's really easy to conquer an opponent's city early in the game, they usually leave their cities lightly defended or not at all.
The opponents also start new cities without any soldiers. I've stopped building pioneers, I just follow the opponent's pioneers around, and then take their new settlements. Even when I'm at war with them, my enemies send fresh pioneers near my territory and start new undefended settlements.
Do the AI opponents have different goodie huts than we do? I started a new game and ran into an opponent. I moused over the AI sovereign and it said he was looking for "empty crates" or something, but he then proceeded to ignore 3 goodie huts (he actually went between them) and went off somewhere else. Needless to say I was happy to then get the goodies huts myself, but I don't think that a very intelligent opponent.