Having played the demo half a dozen times, here is my insight.
Graphics: Better, especially the animations, they seem a lot less robotic and, well, PES-like I guess.
Sound: Yes! The thud has gone. I could hear a lot of shouting from the players too, making you feel you were 'in amongst it'.
Commentary: None, so an improvement over Mark Lawrenson already.
Menu: Looks sharper but more arcade-like. Couldn't care less though personally.
Shooting: I've been hearing a lot of complaining about shooting but it's been fine for me, but saying that, I try to play the game realistically so I don't try shots from the halfway line with my back to goal etc. The ball does seem a bit floaty though, which is a shame as it's been a PES hallmark smacking them in with power from range.
Passing: Brilliant, one of my biggest gripes from 2010 was the poor passing, it seems fixed now and I'm happier with it on this version.
Dribbling: Also really good, I think a lot of people are getting their knickers in a twist about not being about the 'power down the line' at full speed from one end of the pitch to the other but that isn't realistic, is it? The fact is IRL, more often than not, if the defender is in front of you, you need to play a one-two or knock it past him and beat him for speed AND strength. I feel this is mirrored well in 2011. It's been broken since PES6 imo and now seems a lot better.
In ML, for example, you should be able to build a good side without all your players having to be speed demons which became stupid as, in past versions, I'd always overlook a player like Xavi, because of his lack of pace, whereas a player like Gerrard could dribble the ball, rather than pass it, into a better area.
Goalkeepers: Better but still a bit off from what I've seen, a definite improvement though as they don't seem to shovel shots that come straight at them into the net/straight back to the opposition.
Freekicks: About the same so far.
Penalties: I only got the odd one in 2010 and was so scared of missing them, I'd just shoot without any direction. Got one in my first game on the demo and smashed it over. Not a fan of the new camera angle/system.
Skills: Don't really bother with them so can't say.
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Good points: Plays more like a real football game. I love the Referee, he is back having taken a holiday since PES5. I've played a few games on the demo and I can't go back to 2010 now, that says a lot.
Bad points: Floaty ball could become annoying. The replay after every blinking foul is non-sensical and the continued absence (for the most part) of the quick free-kick is worrying. Hopefully, there will be an option to turn the replays off or maybe they are in the demo to showcase the new ref system?