Recently, I borrowed a copy of Tales of the Abyss from my younger brother, and am enjoying the hell out of it, though not as much as I enjoyed my personal favorite of the series, Tales of Symphonia. I wish it had a bit more of the character interaction in it that made me so close to all those characters in the Gamecube game, though Legendia and Vesparia (the other games in the franchise I've played to completion, Phantasia was either too dated or too bad to finish, and I just haven't managed to get my hands on any others) also lacked this. This stuff really fleshed out your place in the world, and made you feel like you yourself had an impact on the way the party interacted with each other (though most of these choices didn't have a REAL significant impact.) Though I do think the general story is better than any of the other games in the series, and I like Guy and Jade a lot, too.

EDIT (After finishing Abyss):

Having now finished Abyss, I really enjoyed it. I don't think it surpasses Symphonia, but that may just be because the time in my life that I played Symphonia was during my personal "Golden Age" of gaming. I like the overall story a lot better than Symphonia, better than Vesperia, (judging by my inability to remember most of the major plot points,) and better than Legendia, although the characters in all three of those are significantly better than any of the characters in Abyss. Symphonia had Genis, Raine, Zelos, Kratos, and Sheena (as far as good characters go, I like Lloyd, but the internet doesn't agree with me there, and I HATE Collette) but I guess it's not fair to ignore Dawn of the New World. They turn the likable characters of Symphonia into a mess of shitty motivations with their horrible stab at fan-service. That game makes me wish it wasn't canon. I mean, is it? Whatever. It's not canon to me.

Anyway, Legendia has Senel, Chloe, Will, Norma, Jay, and Moses (the strongest cast in my opinion, but then again, the character quests flesh them out a lot more than the other games do, and again I'm purposely leaving out Shirly, she's just... bad.) While Vesperia has Yuri, Flynn, Estelle, and Raven. Yuri is probably the strongest character on this list as his murders are some of the most interesting things a character has done in the Tales games I've played. "Great" characters in Abyss seem limited to Jade and Guy, and even though the relationship between Tear and Luke is interesting, the characters themselves are not.

Though the characters in the game were weaker, the overall story resonated with me a lot more than the story in the other games did. And the battle system here is by far the best in any Tales game I've played. The FoF changes make the usually somewhat monotonous button-mashy combat into something much more interesting. Rather than just repeating a combo you've mapped out that works well over and over, you have to actually respond to changes in the battlefield, and pay attention to your surroundings. Also, the enemies seem to hit much harder in general in Abyss, requiring you to be more attentive and actually control your healer a bit more than the other games, which I think is a good thing.