The pes demo doesn't look a whole lot better than pes 11 but it's "early doors" as they say.
As for you guys experiencing problems with the gameplay and AI in pes, I can't relate. Just a thought but maybe it's down to your tv I have a great tv for playing video games on a Samsung c530 and it runs very smooth and the input lag is extremely low. I also have a high speed hdmi cable I got off amazon for < than 10 euro.
It's not lag, it's more the positioning of the players and the lack of accuracy in passing. Also more expensive hdmi cables are no different to cheap ones, it was proven.