The reason why its not spammable is that the health threshold needed to use a limit goes down every time its used, so it becomes harder and harder to use, and might even become unavailable.
The limit attack can be used when your HP goes into the yellow range. Then, you can use your limit while a white line acts as the timer by going across the empty portion of your HP bar, so the more HP you lost, the longer you can use the limit break. After every time you use the limit break, the yellow portion decreases so it becomes harder and harder to use it.
It seems that different weapons cause different combos; Axel's standard Chakrams cause his standard attack, the second one seems to be have a greater area of effect, and the last (which looks like its Lexaeus-themed) has slow but powerful one hit combos.
I doubt they'll have FF characters given the nature of the game. They'll probably have more of a huge enemy boss, like Sin from FFX or various Weapons from other FFs.
I believed the Roxas battle was confirmed to be a mental battle.
Could Sora really have been a heartless through CoM? I thought some Organization members stated he WAS a heartless, but not anymore, not to mention that Sora was missing some traits of heartless.
Edit: Also, Namine isn't a nobody according to DiZ: She is a "non-being" in the truest sense of the word; having not even become a Nobody and with nowhere left to go, she is but the most fleeting of shadows.
Yeah, that fight was awesome, the Melee part of Xaldin's DM just did Xemnas in. Although the beginning was rather boring; Xemnas would start a combo on Xaldin, Xaldin would attack, but Xemnas wouldn't flinch, Xaldin would get owned until Xemnas stopped, at which point Xemnas got hit back by the wind, and repeat the whole cycle.
It looked like Xemnas's DM could have hurt quite a bit, but Xaldin only got hit by part of it.
BTW, have you guys ever thought of putting an Invincible Sora with sucky stats in there, just to cast thundaga on things with 0 HP? That'd count as a finisher, right?