Okay, first to clarify my previous post. I didn't hate the ending. It wasn't the strongest point in the story, but was completely serviceable and didn't leave me disappointed.
With that out of the way, here are my spoiler free impressions after clearing the whole game.
I'll just mention it again - clearing ToB took me 48 hours on Normal. Tried doing all the side stuff I could find aside from the last batch before the final dungeon. There's also post game content including an extra dungeon, but I haven't touched that part myself.
Graphics
It's definitely the best looking 3D Tales game. Sadly, that doesn't really mean much. Models look alright, but in the end it still looks and feels like a PS3 game bumped to higher resolution and 60 FPS. Fields and dungeons are a mixed bag, some look good, some (especially early ones) are just boring. Also, the draw in distance is terrible and nothing really excuses this in the PS4 version.
Sound
I liked one of the themes (main/Velvet's theme?) which kicked in during some cutscenes and made them more exciting. Also,
theme was great, but I think it hasn't changed. That said, I'm a person who rarely focuses on BGMs while playing, so don't take the above as a jab at the music.
Combat
Combat doesn't really change through the game. You get access to some new toys like Mystic Artes, but aside from that you can still pretty much mash through every battle on normal with X and R2, if you're not hugely underleveled. Problem start if you don't get enough souls during your mashing to activate the Break, since it's Velvet's main way of regenerating HP. When that happens, you have to charge block and attack, use Mystic Artes (they add souls) or switch characters back and forth.
I enjoyed the combat system for what it was - flashy, fast, and relaxing, but I think people who want more to put more thought into each battle, turning the difficulty up might be necessary (although Bebpo mentioned that not much changes).
Story
This is where the game shines. No forced romance between party members. Playing as the "bad guys" which will use all means necessary to get what they want. A lot of very dark and sometimes even depressing elements, while never going too far. The story really felt like a breath of fresh air compared to most other jRPGs. While the start is slow and might feel like "forced edginess", it definitely gets better later.
Is it perfect? Of course not, there are still ups and downs, boring moment etc., but in general I think I enjoyed this story the most of all Tales games I've played. This includes Vesperia, but to be honest I cleared that one so long ago that I don't remember much.
I also like connections to Zestiria, like explaining some things in the world. I would definitely suggest finishing or at least playing a bigger chunk of ToZ before Zestiria, if only to catch those parts.
At first they feel like a boring bunch, with less jokes in skits than in previous games. That said, as time goes on they open up and the player can see that they have their own quirks, things they're passionate about (not related to the story) and are all in all quite funny.
The cast really grew on me, even annoying at first Magilou.
Dungeons, Towns, Fields
Dungeons and fields for most of the time were boring. While I liked that they got rid of huge open spaces from ToZ, they still felt like corridors randomly sprinkled with enemies. Some looked nice, that's true, but in the end running through them felt like a chore. Especially when I had to do it multiple times for side quests.
Towns were alright and I liked how the atmosphere changed as the story progressed (mostly NPC dialogue and some effects, buildings etc. stayed the same), but again - running through them multiple times got boring at one point.
Final verdict - a really good JRPG, one of the best (if not the best, probably will be a personal preference) 3D Tales games, which loses some points because of being a cross platform game.