Does the battle system include my favorite SaGa trope, the whole learning abilities randomly in battle thing? I love that, for some reason.
Yep. Except this time, you've got Unions that you put together (think Ogre Battle), and there's the potential of any of your guys learning new moves (or upgrading existing ones).
Leveling is also a little different, it's like the earlier games where you just increase stats seamlessly, but there's also something called "Battle Rank" and "Chains". Your Battle Rank determines how "powerful" you are, although it doesn't really work quite like that. If you take on lots of enemies at once and get your Battle Rank up too high too quickly, then you stop getting stat increases from the enemies you're fighting, and it leaves you underpowered. The Chains, if I recall, are how many enemies you take out in a row without getting surprised or whatnot, and affects battle loot.
Anyway, the best way to play is to take on single enemy encounters, to give you more battles by which you can increase your stats before your Battle Rank goes up. Definitely don't do the aggro thing where you draw them all in at once, that's typically a recipe for disaster.
Oh, the music in the game is also phenomenal. The battle music, in particular, is noteworthy for literally rocking out.