After playing 10 or so games of demo 2, I cannot agree with some here saying that this is the best PES ever.
While there is undoubtedly potential for a superb game with what they have here, a few things ruin it to a certain extent and put it more in the 'close, but no cigar' territory.
First major problem is defensive AI, particularly positioning. Defenders do not keep a flat line, no matter what settings you play with. They track opponents deep into their own half, making the defensive structure fragmented, and thereby too often creating unrealistic gaps and space for the PC AI to play with (And it actually goes both ways). As a result, you almost never see any offsides (I've seen one). It also leads to lots of 1v1 chances from nothing...just have your CF make a run, the D will track him the whole way back, making it a 1 on 1 (CF-CB), put in a through ball and more often than not you get a scoring chance.
The next issue is the overpowered dribbling, particularly star players with the speed merchant card. Play with Bale and you can run past and through an entire defense with ease, much like Fifa of old and PES2008. While there is more balance than demo 1 for average players, the superstars are just too good. Add to the fact that there is more error built into passing and that passes generally move slower, the game rewards direct dribbling rather than creative build up play. With it also being more difficult to tackle players and with referees calling more fouls, there is no doubt in my mind that online/multi games will be dribble-fests.
Other smaller issues, like super potent FKs, so-so Gks, slow reaction times and relatively poor agility of players without the ball (seems like players are faster and more agile with the ball than without), players lifting their feet rather than blocking weak passes... are things I can live with. But the above two points really take the realism out of the game.
And its a shame really, cause Konami have been on the right track for 2011 and 2012. Oh well, like every other year....maybe next time they'll get it right.