I agree with most reviews on this, there is a noticeable increase in difficulty throughout the game. However, persistence is the key and after 2 or 3 hours of play, you start to work out the new features and how the game insists you deal with them. The new defending system has brought a new dimension to the game and having good defenders who can anticipate the play helps enormously (not really required on previous versions as all you had to do was plough into the attackers to win the ball back). This time you need to think positionally and not dive in to tackles as you would if playing the game in real life - some people may not like that as there's admittedly less fun in defending than flamboyant attacking play. However, it does instill a sense of acheivement when you jockey your opponent, anticipate his movement and make a block or tackle. The pace of the game is slightly slower (by default) but you will need this extra bit of time to defend properly, experienced players can of course increase the speed of the game.
Attacking is excellent as usual, with the welcome addition of being able to hold a shoulder button to execute a skilled pass (backheel, flick etc). Crossing has also been overhauled and needs to be relearned, especially with no instruction manual in the box but again, is an improvement on FIFA 11 - I scored the majority of my goals with headers last year which is a little unrealistic. Graphics and player likenesses has been dramatically improved and the commentary so far seems marginally better (though you need to play the game for a few weeks before you start noticing the repetition!).
My only major complaint is the fact that you are still unable to play career mode with a friend over xbox live?? This is something which EA dont seem to think we'd want, but personally, I prefer to play on the same team as my friends as opposed to against them - this is probably more appealing to the older gamer like myself who doesnt obsess about 'beating' my friends at games but enjoys the social and teamwork aspect of what the game can offer.
If I could, I'd give the game 95% for this reason, but otherwise, any football fan should buy this game