Lots and lots of updates on the main site. Looks promising.
http://www.namco-ch.net/xenosaga2
1) Basic gameplay mechanics is mostly unchanged from Ep1. Segment door puzzles, assembling the ultimate robot puzzle, traps on the maps that can be triggered when enemies get close, etc. A slight change regarding destructable objects - different characters will have a different animation.
2) Additional minigame called the "G2 campaign" - a series of 36 mini-quests that involves helping NPCs with various difficulties.
3) Those with the demo may correct me on this - but it appears that it is no longer possible to get on and off an ES whenever desired. Dungeons are either character or ES-based.
4) Additional field effects(already reported by IGN) - attacked unit gets a boost, attacked unit loses a turn, Ether effect +50%.
5) Reported long ago - combo attacks.
6) A max of 3 characters are allowed on the battlefield. However characters can be switched in and out in the midst of battle as often as desired.
7) Each ES unit has a special property to make it unique. For eg. only Momo's ES can cast Ether spells.
8) ES units are 2-pilot units. It has been revealed that Jr, Momo and Kosmos are the main pilots of their respective ES. The other characters are assigned to be "sub-pilots"(maybe they meant co-pilot) of these units. The special attacks of an ES change depending on which sub-pilot is assigned to it.