I finished Trails Through Daybreak last night. It was mostly a good game, but I have problems with the story. I don't want to go too much into it, but it's much simpler politically than the other games in the series. And the main villain's intent is really simple. That's a big minus in my book.
However, I really like most of the changes made to the combat system. When I first heard that they were introducing field combat to the series, I thought it was silly and thought I'd never use it. Instead, I found it very useful and engaging.
The shard system is also pretty good. It reminds me of the older trail games where you had quartz lines and got arts depending on the element of the quartz you had on them. Instead of having different arts, you gain something else called shard skills and lines correspond to different categories (weapons, defending, arts and EX.) I found myself moving quartz around to get certain skills on certain lines.
S-crafts are kind of a mixed bag. I found it strategically interesting that they made S-crafts depend on a shared party resource called the boost gauge, so you can't just spam them willy nilly like you could in previous games. However, I disliked how they got rid of strategic timing of S-crafts with regards to stealing AT bonuses on the timeline, so I was mostly spamming attack based ones whenever.
The music is pretty good, especially the dungeon themes. I think the final dungeon in this game might have the third best final dungeon theme in this series.
As far as characters go, most of the playable characters are pretty great, personality wise. I did feel like I wanted to learn more about some of them, but I suspect it will be revealed in later games.