I don't think Locomotion will do much of anything to improve the gameplay. It simply a momentunm-based animation for the players that still look artificial and clunky.
The player models don't react and interact realistically in the first place - why should anyone get excited about them accelarating and decelerating when they still look strange and robotic?
If anything, it'll finally give Acceleration ratings a purpose to be in the game as more then just a fake number to affect a player's value in a CPU-controlled draft.
(Sorry I'm so pessimistic. I'm just tired of waiting for EA to make a decent football game. Locomotion, Pro-Tak, etc... they're wasting all of our time just adding these "features" to an outdated animation-based engine.)
EDIT - they've been struggling with acceleration/deceleration for years with Madden. We're talking about basic on-the-field player movement and every other sports game has it down pretty good - but for some reason, EA can't get NFL football players to move like they do in real life.
That reason is the engine itself. The players move around the field as if they are on an invisible, floating disc - and their collision is based on their discs bumping into another player's disc. So with that visual, they try to implement locomotion... the player on the disc has to somehow synch up with the momentum they're trying to simulate and still look like they're actually moving based on a center of gravity. It's not working IMO. It never has in Madden. It always winds up looking like the players are on some strange swivel and their arms/hand/legs never seem to flow loosely, like they did in the 2K games when a player juked or came to a sudden stop.