I played the demo prior to release and I was reasonably impressed. However, I firstly want to make clear that THIS GAME IS NOTHING LIKE THE DEMO. So if you choose to part with £40 on the strength of it then you will, perhaps, be disappointed.
The problem with this game, in my opinion, is to do with two things. The first is that there isn't a difficulty level that suits someone who is able to play the computer reasonably aggressively but, on the other hand, is not one of the die-hards you might happen to meet online who will beat you 10-0 every time.
On Professional difficulty, it is too easy to rob the computer of the ball (particularly the last defender), but at the same time it is simply too much of a toil to score. Many reviewers say you have to pass the ball and work an opening, but I have to say that even doing this results in a very frustrating experience. I only play 5 minute halves, and I regularly find that I can play two or three matches in succession without managing to score. If I do, then it is invariably due to the "robbing the last defender" scenario, which isn't a very satisfying way to score.
Increasing the difficulty to World Class results in a more challenging defensive experience, but the computer's defensive capability becomes spitefully hard. You get nanoseconds to decide what to do when you have the ball, you cannot outrun opposition defenders, passes around the edge of the penalty area whilst trying to "work the openings" are almost always snuffed out, and the computer seems to be able to hold your players off when you challenge for the ball - something you do not seem to have the option to do when in possession yourself.
The second issue is perhaps most frustrating of all. After having persevered and battled through the above spiteful frustrations and you find yourself bearing down on goal, the shooting system totally lets you down. I expected the 360 controller movement to enhance the placing of shots. However, despite the fact the goal is 18 feet wide, every shot seems to be fired straight at the 3 foot window either side of the goalkeeper, regardless of where you push the stick. On the replays it is clear that even when you score, the ball goes under the keeper's arm or under his body; the ball rarely flies into the part of the goal that is out of his reach.
So when you eventually bear down on goal, the keepers make unlikely point blank range blocks more frequently than is perhaps realistic or fair (given the effort you have put in to get into that position). The only reliable way to score is to build up your attack to such an extent that you are squaring the ball for a teamate to tap-in to an open goal. To do this is particularly hard, and when playing 5 minute halves you will find yourself grinding out 0-0 draws on a regular basis.
This is a game. It is played for enjoyment after a tough day at work, and I think EA have pandered to the hardcore in making this unfairly difficult and frustrating to the point that a goal no longer brings enjoyment. It simply takes the edge off the boiling annoyance that has built up inside you from being persistently outwitted by the computer through jaw-droppingly unfair AI.
Unfortunately PES 2010 didn't look too good either for different reasons. It's disappointing there are no challenging but ultimately rewarding football games out this year.