If you have a recent edition, don't rush out to pick up this marginal "upgrade" on a stagnant franchise.
Most of the changes EA made to this year's edition come in Franchise Mode. However, they largely feel experimental and almost all of them need tweaking. To give a quick rundown:
Expanded Preseason Rosters - This feature is good but doesn't add much to the game. Essentially, you get to carry many more players during preseason, while making cuts each week to get down to your eventual 53-man squad.
Free Agent Bidding - You no longer have the luxury of negotiating with any free agent you want, with as much time as you want. Now, you must bid against other teams within a limited time frame. One the one hand, this adds more urgency to the free agency process, as you rapidly scroll through menus identifying the best free agents and how they match up with your own needs. However, this excitement comes at the expense of realistic flexibility -- you can bid up only the total dollar value of contract, without adding or subtracting years or bonus money. This is extremely unrealistic, since in real life teams always have the option of enticing a player by offering them more bonus or more years. This slices down the set of incentives from three (total money, bonus money, length) to one, and is typical of Madden in the PS3/360 generation: one step forward, two steps back.
Scouting - Scouting is now an elaborate process that demands more attention throughout the season. However, a few cheap exploits or tricks (particularly sorting all players by Potential, which still works) insure that you can draft half the superstars in any given draft (including all the late-round gems) effortlessly. This is pretty poor game-building, and doesn't fix the problems of earlier versions in this regard, only dressing up the same broken system in newer and more inconvenient clothing.
All in all, this game is still fun, as it has been for many years and always will be (particularly to passionate football fans like myself). But it is, undeniably, a flawed game.