I didn't like Vesperia that much as a long time Tales fan. The main lead was amazing and the game looked nice but the battle system got boring by 40 hours in or so and the plot was pretty bad in the end 1/3rd where it became about the summons and random boss for no reason. Basically it was great for 30 hours or so and then less than stellar for the last 20.
so - it fell apart after 30 hours, how do you know Graces won't do exactly the same?
How many hours in are you? I am mildly interested in Graces.
Graces is only 30 hours long

I'm about 20. The thing is the battle system in Graces won't get boring because you don't max your skills early on. The problem with Vesperia is you learned all of your moves in the first half of the game and then it's like...no new moves for 30 hours. So you're just doing the same combos over and over. Some Tales games have a small moveset and suffer from this problem. Others have very large movesets and don't. Graces has a large move/ability set and is spread out nicely. You have about 120 titles to learn 5 skills each from and it takes a battle or two or four to learn a skill. So you're constantly getting a new stat, move, ability every other battle which keeps the game fresh and there are so many stats that you'll never learn them all by the end of the game. Plus since you can choose which title you're learning from at any time you have a lot of freedom in developing your character.
Also there are very few encounters compared to other Tales games. I usually finish every Tales game with about 1000 battles fought. I'm maybe 2/3rds through and I've grinded a bunch and I'm still at <500 battles fought so far. If I hadn't grinded I'm guessing I'd be around 300-400 battles fought.
So less battles, shorter game length (Team Destiny games are always about 30 hours for the main story and are tightly paced as opposed to 50-60 hour TS games with more padding) and tons more moves/abilities to learn = doesn't get dull.
The story could take a nosedive. It's not particularly good. But it's a decent animu narrative with good party characters. All the Tales games have bad stories & great party characters outside Abyss which actually had a good plot and maybe the first half of Vesperia's plot. In the Tales group of plotlines, Graces being non-fillerish and following a standard narrative alone (without furries or racism) makes it one of the better ones.
Art design-wise it has more in common with Abyss than Vesperia did with Abyss. Graces's cities are colorful like Abyss with lots of rainbow sparklies and greens and water. I prefer that style over the darker purples/browns/greens that Vesperia used. Graces animates better. But Vesperia obviously has the cool cell-shading and clean visuals.
There's a good chance Graces will get a visual boost when it's [probably] ported to the PS3 later this year too