Single player AI is kinda "Eh", but most people are buying it for the multiplayer which is very solid. If you're looking for a title to start up your PS2 Multiplayer Connection, it's fairly good (not as good as Madden, but obviously much different), but if you're looking for something to play on your own, there are other better games out there.
If you are playing single player, it's fun, pretty good, but as the post above me says, there is better out there.
However, having said that, if you have the network adapter and a broadband connection, this game is crack. It's a blast. And the little headset things for me have been clear as a whistle, contrary to reports on Penny Arcade.
oh come on now boy think / what would jesus do / he'd shake his head like a angry mother spoke the boy / he say do what i could do / you take care of it please / but it's the only one you got / and it'd take ten lifetimes boy / to undo what i've done