If they'd kept the foul system from the demo, online would be a very different place.
Definitely.
Playing my mates on the demo (most of them don't own the full game) is a joy - they generally overcommit/pressure often, and I can either jink away from the challenges and tear through the defence, or manoever the ball into dangerous areas and then draw a foul (especially with Iniesta/D'Alessandro/Messi/Robben). Usually this allows me to score at least one goal and dominate the game.
In fact I've only lost to my mates about 5 times in probably over 50 games on the demo, these are experienced FIFA players as well, no mugs when it comes to gaming.
The full game is far more biased towards the defence - the (auto)tackling is seemingly far easier and the amount of fouls is much lower. I think the short passing may possibly be slightly more assisted in the full game too.
Just seems more "noob-friendly" in general, and that's disappointing.
In the full game, I generally have less success in multiplayer, with games being far more balanced between "gamers" and "footballers", although I still end up winning more often than not, I have to sacrifice the silky dribbling for more quicker passing to players in space and don't score such a large variety of goals.
Another thing that may be a placebo effect - R2 controlled shots from distance seem less powerful in the full game.
I've scored one with Villa (vid below), and scored a sweet goal with Messi on the demo a few days ago, beating a couple of players with R2 dribbling, then bending it into the far corner from about 25 yards with the keeper flat-footed.
R2 shots are delightful from within or just outside the box, especially with the technique players like Del Piero, but it's rare to trouble the keeper from any sort of range.
Maybe it's because they were with world class Barcelona players rather than the MLO/Coventry players I usually control on the full game...
That goal;
YouTube - PES 2011 - David Villa curling strike
Don't get me wrong, PES 2011 is still a footballer's game, unless the "gamer" knows the game inside out and has played it a lot. When I'm on form, I'm capable of beating D1 players online who have a win% of about 70% after 1000+ games, in no other football game has that been the case for me, even PES5.
In PES5 it was the long chipped through balls from out wide with Beckham/Ronaldinho, PES6 I'd get raped by Adriano/Inter/cutbacks, FIFA 08-10 I'd get raped by speed demons/ping-pong passing/pressure/finesse shots. 2011 has the speed merchants and at times unstoppable passing moves, but whenever I concede I can usually look at the replay and find something I could have done to prevent it, there's far less rage involved this year

.
I'm still really enjoying PES 2011, probably because I havn't overplayed it, but Konami could go on to produce a spectacular simulation next time around, if they don't give in to the demands of the casual players.