Famitsu came out with new information on Lightning Returns: Final Fantasy XIII's battle system, as well as additional details.
First off, the different costumes Lightning can wear aren't just for show. Different costumes enable different properties and attacks, and it appears it is comparable to switching classes. For example, wearing the Black Mage costume improves her offensive magic and gives her a new ability called Thundara + Aerora. Thundara + Aerora combines wind and thunder powers into something more powerful. You will want to choose your costumes carefully based on who you're fighting and in what environment you're in.
Lightning's other abilities include area sweeps and counter blows. Area sweeps are melee attacks, useful when multiple enemies swarm you. Counter blows are executed just before an enemy hits you. They consume a lot of your ATB gauge, but can increase the chances of a knockdown.
And then there's another mechanic reminiscent of Monster Hunter. Certain monsters get impaired when you cut off a tail or strike a specific area. Even if the monster doesn't get destroyed, if you are succesful in your strike, you can be rewarded with items.
You need not fight monsters out in the wild. Yusnaan has a private Colosseum, called the Arena Slaughterhouse, where your enemies aren't always human. It's possible that this area is set up to be a training ground, or it's just a place to help raise your experience. The game is open ended so you can presumably come here anytime.
Finally, Famitsu rounds it off with pictures of the cities warehouses, that store many goods. Nothing much added to that, which makes you wonder how the warehouses will be factored in later. You can check out all the pictures below, courtesy Famitsu.