Initial impression: Xillia seems aesthetically inspired by FF13 in many ways. The character models are only slightly more detailed than any of the previous Wii/PS2 games (it's still very anime-ish in that regard) but the environments are much, much nicer and with attractive designs. Now that you have camera control and can actually look around the environments, they encourage you to do so by hiding random items in little sparkly hotspots in various places around each map. There are also area maps you can peruse at will. Also similar to FF13 is that most NPCs are non-dialogue. The ones that are have an icon over their heads.
Also, the chat system has been redesigned so that small comments about each area/latest story developments are spoken on the fly (with subtitle text in the bottom left corner) as you are walking around. Longer chats have the usual select button prompt, but you can replay them at any time from the menu.
Battle system moves away from the Graces system to more like Abyss/Vesperia. There is L2 free-run and a CC counter for physical attacks, but artes/special moves cost TP again. I haven't gotten far enough to test out the new "link" system very much, but in short, you can have another party member team up with you, circling around to the rear of the target for combo attacks. Each member has a special ability they will do when linked if you press R3 (i.e. heal you).
Character progression is again, a lot like FF13, with a six-sided grid corresponding to each of the four main stats. Every rectangle bounded by four nodes has some skill or magic inside that is unlocked when you have selected all the nodes. Seems like you get 3-4 points for every level. Again, similar to A/V, skills can be equipped and your total skill points pool increases by level.
Also similar to FF13 is a more streamlined shop system. Five kinds of shops: item, food, weapon, armor, accessory. Each shop type is basically universal–it stays constant no matter where you are in the game. However, you can unlock more items and discounts on items by leveling up the shop, which you can do by either: buying or selling stuff to the shop, paying gold directly for points (i guess maybe it's a better exchange rate than if you buy actual items?), and turning in ingredients that are found on the map or drop/steal from enemies. Not sure if there's another use for these such as alchemy/forging but there are a couple different categories of ingredient, and each shop will have some bonus value associated with one of them at any time, i.e. double points for "beast" ingredients, so you can streamline your upgrading in some ways.
Grade is sort of trophy-related. Rather than getting any for battles, there are a variety of categories (items/monsters seen, highest combo, artes used, time spent in link mode, highest level, shop level, etc etc) that will reach various checkpoints as you keep playing that will pay out amounts of grade. So fight 10 different types of monsters, get a 10 grade bonus, which unlocks a 30-grade bonus for fighting 30, and so on. Eventually I think you reach some level that also corresponds to a PS3 trophy, but they incentivize the progress by giving you these grade payouts at intervals along the way.
I'm not sure what other stuff is in the game because I'm still mostly in the prologue section. Oh yeah, also similar to FF13: the story is sort of cryptic and opens in media res. Definitely a bit more interesting than the usual Tales fare in terms of setting up the story. I'm sure it will turn to schlocky crap eventually, it is a Tales game.
I'm certainly not far enough in to say if I've got a perfect grasp of everything the game has to offer, but I feel like, while it's definitely a finely-crafted game and has a bit of that "wow" factor that Vesperia had as the first next-gen Tales entry, I feel like it'll be hard for Xillia to top Graces F for me. That game is another level in terms of "yarikomi" (deep completionist) content and I'm at 140 hours without having beaten the initial game yet, whereas Xillia seems less involved and complex. There are fewer systems to keep track of, and there are some things, such as the return of elemental properties being weak/strong/absorb style (as opposed to Graces' awesome idea of only enabling bonus damage for weaknesses, so either you took advantage of elements for extra damage, or you ignored them and did normal damage; it would never actively hurt you by healing enemies and bullshit like that).