Playing online can be incredible, but only when you've got two good players using non-superteams, with pass assistance on zero, trying to play realistically. The difference between that and the fully-assisted, 100mph-pressure, speed-merchant hell of most online games is so great it boggles the mind.
Anyway, as soon as you pick those 5-star teams the game automatically becomes arcadey. Any attempt at a slow, patient, tactical game with those teams turns out like some kind of sped-up circus show, whatever you do. Their skills and speed are just so pumped up that it's pretty much impossible to get a decent, realistic game out of them - they're only really any good for 14-year-old inadequates who have no interest in playing a representation of football, only winning at a video game. Those Barca freaks are like an 80s caricature of a gamer, staring blank and glassy-eyed as they blast away at identical ranks of Space Invaders. Hate to be them.
Pass assistance is the other thing. A 1v1 game on zero bars is a thing of beauty (once you're used to it, and stop sending simple 5-yard passes slamming into the advertising hoardings). You have to work for every goal, the final ball becomes all-important and requires real concentration, the game has a realistic stop-start flow that you just don't get when you use any kind of pass assist. But the only way to get regular zero-assist games is to join an online league like PEEL, because you sure as shit aren't getting them in the regular lobbies, and it'll be a chilly night in hell before you get one in MLO.
PES2012 online is weird. Depending on who you play, which teams you use and how you have your assists set up, it's like four or five completely different football games. All but one of those games are appalling, but I reckon one is the best of all time. The fact that 99% of people on PES online would rather shave their balls with a cheesegrater than play it, just in case they don't win - that says something pretty rough about humanity.