Fantastic game. The game runs great, I've encountered no bugs or bad AI, and the battles are epic and engaging.
First off my computer has an i5, HD 7850, and 8GB of Ram. I have the graphics fully maxed out at the highest setting. This game runs smooth, no lag, and looks great. I can have my army at its max capacity, an ally's army at it's max capacity and the enemies army at max capacity and battling at once and it still runs great. This is 2013, if you can't run this at any setting without it playing good then it's time for an update. My computer isn't even at the highest end of what's considered powerful.
Secondly, I've encountered zero, zip, nadda, no bugs or problems. The AI, has been good, and had a share of losses when I wasn't prepared or thinking. The enemies attack, defend, fight, basically do what they're supposed to do, expecting anything more from AI in a game of mass proportions is absurd. In no way has the AI ever acted in a way that has ruined the game or caused me to even take notice.
And now the game, it's epic, detailed, fun, time consuming, engaging and just plain incredible. I find myself leaving the real world and getting lost in it, turn after turn. I had to stop myself before my muscles turned to mush. If you would like to know what it feels like to command a massive army and fight an epic battle for the sake of Rome...get this.