So, let's see...
- No Team Ranks
- Partner Pokemon easily lose track of you and wander off, even in tight corridors
- The game throws a Level 20 High-Tier Pokemon to you for free
- You can't do more than 1 mission at a time
- Mission rewards are very poor, due mainly to Team Ranks being gone
- Shared EXP, even among members not in the dungeon, reducing grinding and replayability
- Text Speed is still just as bad as it was in the demo
- Game forces you into the Nickname screen every time you recruit a new member
- Recruitment Rates greatly increased, removing the grind to gather new partners
- Story Dungeons broken up by "Press This To Progress" environmental "puzzles"
- One, fun looking Boss Battle was ruined and made too easy by half the current cast showing up to help
- Multiple shops that all sell similar items, making you run around the whole town between missions
- The level's grid is hard to figure out without turning the grid itself on permanently (Do NOT try doing through a dungeon with the Circle Pad... you'll fly all over the place)
- No water or abyss portions yet, and the Litwick I've encountered have not been able to go through walls (mechanics taken away, or possibly I just haven't seen them yet)
On the opposite end of the spectrum...
+ Move Levels increase a Move's PP, fixing one of the previous title's issues
+ Team Attack is useful for clearing out annoyingly crowded rooms
+ Dungeon Generation is getting better as I progress
+ Characters are still lively and personable
+ The difficulty is still very much there
These are my observations from the past couple of hours.