This review comes from the perspective of a user who has had the game for just over a week now, is playing as the Gunners in Manager mode, and has so far not tested it out online.
To make this simple, as there's a lot to say, I'll just review each of the points, and then conclude.
MANAGER MODE: Personally, I'm a fan of the Football Manager series for PC - what I wanted from FIFA was to incorporate some of the strengths of this into a format where I can control the players instead watching from afar. This is only partly achieved. The negotiations, board interaction and new transfer budget adjustment system are all more realistic, but as far as I can tell, scouting has been removed, statistics are only confined to seperate competitions and so not obtainable overall, and the advice you get from the Assistant manager is regularly garbage. The news system, which was in the world cup game, is a nice addition however. Also, the first season includes no European comptetion, gutting for Spurs fans - and I can only assume this is due to licensing.
Ultimately, Manager mode doesn't draw on some of the positives from the other FIFA games, for instance in either 2010 or 2009 (can't remember which) you can swap players' squad numbers. In 2011, as Arsenal, starting with a vast squad, I don't know if I'm giving a youth player someone else's number or not, without scrolling through the more obscure players of my time. I miss that little number grid.
WHO TO BUY?: Well, at this stage, no young players. They don't improve! A quick google search shows that this is a glitch in the game, that would have really put me off had I been aware of it before the game was available for purchase. Jack Wilshere for instance, in real life a rapidly improving player, and arguably the future of the England team, has so far started about 20 times for me, and has got no better. Similarly Neymar, possibly the best signing to make on the game (if improvement worked) has been regularly starting, scoring and assisting, but is still not improving. Gutted! Especially with Arsenal, who have a wealth of young talent included in their FIFA 11 squad. Watch out for deadline day, too. I made two contract offers about 3 or 4 days before Feb 1st, and a week passed completetly oblivious to my transfers. Bye bye Jack Rodwell. No midfield partnership with Wilshere and Fabregas for you this season.
GAMEPLAY: Tricky. The passing system both does and doesn't work. Through balls are regularly played directly to defenders, no matter how specific you are with the little joystick and the supposed 360 passing system. The strength of the passes is also extremely disappointing. Again, playing as Arsenal, and trying to replicate their real life style highlights these problems. That said, when you get the ball zipping about, the passing feels good and smooth.
As for defending, my DMF is finally making tackles, whereas he was regularly bypassed in 09 and 10. Midfield battles are more important in this FIFA, and tackling is a far more contested area of the game. This is a huge plus - as it makes the game far more realistic.
However, where the game loses realism is in the opposition. Too many times I have watched John Carew casually stroll up to my goal when 1 on 1, only for Squillaci (who, incidentally, the commentators give some random German-sounding name to, a one-off as far as I can see...), who's not the quickest player ever, to stride up alongside him and nick the ball. What's also noticeable is whether you play Wigan or Barcelona, the style of play is always the same. You effectively play the same football team each week, just with fluctuating levels of ability.
Shooting is OK, Arshavin's trademark low drives are tricky to execute on the narrow angle, and scoring outside the area, although possible - is very unlikely, especially with a crowded box. The keepers are at least far more realistic, jumping straight back up to make reflex saves. Free-kicks, as ever, remain something of a lottery, but corners produce goals more often, and the new penalty system is excellent.
FIFA's big improvement, the personality...thing is only partially evident. Playing with Abou Diaby is a revelation - even at DMF he gets up into the opposition box and bangs in 10 headers a season, after winning the ball back in your own penalty area. However, try an ambitious pass with Fabregas, and it may as well be Manuel Almunia. There are, however, obvious differences in playing style for various players, which is a plus. It's often suprising who this does and doesn't affect. There's nothing seemingly special about Mesut Ozil, or even Kaka, but Henri Lansbury plays with a suprising smoothness, and Laurent Koscielny often gets himself in a muddle.
LOOKS/SOUNDS?: The music selection is again wierd. Some awesome tracks in there, I often find myself fiddling with my tactics, just so I can listen to more Gorillaz and Two Door Cinema Club and get away from some of the more appalling tracks feautred on the game. Go to the EA Trax section to get rid of some of these monstrosities. As foor looks, the game looks great, the cardboard crowd get no close ups anymore, the commentary is less wooden and helpful stats pop up from time to time. The refs even have names, but they're all a bit silly. One slight annoyance is the 'scores from other games on at the moment' feature, which blocks your view if you're running up a wing - and should only really be of any use on the last day. I don't care that Blackpool are one down away at Everton in Week 2. The general feel of a matchday is excellent however, the chants, though infrequent, are there - and the player likenesses are often freakishly accurate.
OVERALL: Frustrating. It is very good, but it leaves you wondering how they can make some really great improvements, and then ruin it all by not allowing young players to improve. The opposite was true of FIFA 09 - I got 30 year old defenders improving by six a season until they hit 32, and 19 year old forwards improving by 12 until they hit 21. In FIFA 11, seemingly random players increase or decrease by one or two - and this really spoils manager mode.
Hopefully an update will be available for this.
Until then, my advice is this - you will enjoy FIFA 11, more so than 10 for sure. But be prepared to be annoyed on occasion. Decide whether or not this is worth the price.