Woot...finally something I can contribute to! Some points:
-Ya can still lvl like mad off of Dolls in Zot, and that summoner in the sylph cave. And of course, killing the party after ya become a pally on the ordeal mtn still works wonders for training.
-There are 2 brand new areas! One opens up in Ordeal mtn after the Babil situation....there lies special eq for the switich characters..as well as stuff ya can't find anywhere else. The other is a 50 floor final dungeon on the Moon that can only be accessed by the specific party ya beat the game with....containing even more "only there and FREAKING awesome content/stuff"
-Many characters can gain upgrades to their special powers...for example...Edward's Sing becomes Chant...whihc casts Shell and Protect on your entire party
I'd go on listing more...but it'd be far easier for all needing info to chekc the thread over at Gamefaqs.
Glad to help a little regardless though.