He show's you his floatie homes 

Graphics from Gates to Infinity carry over, with all the major problems of GtI, such as the lack of Pokémon variety, being fixed.
Personality quiz is back, while not completely restricting you to the Pokémon you end up getting on the quiz. This is a very nice feature that I'm surprised wasn't implemented sooner.
Mixed-and-matched elements of all of the preceding main series of PMD seem to be used; R/B Rescue Team is definitely seen during much of the Serene Village arc, the attendance of the School and Expedition Society, along with the Voidlands arc, felt very Explorers of T/D/S-esque, and the overarching plot and final dungeon were very reminiscent of the GtI plot.
This game's main story is FAR more difficult than any other I have played. I completed the main story at Level 26, far lower than any other, and the level curve is pretty brutal. Nice for a challenge.
At the same time, the game grants you high-level Pokémon that you can recruit from the very beginning (if the Salamence mission wasn't any indication... *shudders*) while also forcing you to use your lower-level Pokémon often by making the powerful ones only usable every so often. This is also interesting and a great way to get the player to not simply rely on their powerhouses.
Immunities are indeed immunities now. Was that a thing in GtI? I don't remember.
Connections are a nice way of putting a spin on rescue-and-recruit missions while maintaining the whole idea of going to a mystery dungeon to complete missions. Kinda miss having rewards, because I find myself running low on money a lot...
Almost every single side character travels with you through one dungeon. That's pretty nice for character.
The gold exchange shop...whatever it's called...is a really nice feature. It grants really easy access to Reviver Seeds, which are ABSOLUTELY NECESSARY in this game.
Alliance attacks are fun.
The original soundtrack of this game is very nice. Sometimes a little out-of-place, but still quite nice.
The remixed songs (like Great Canyon, Crystal Cave, and Amp Plains) are really nice, and the soundtracks that they brought back are some of my faves (Northern Desert, Forest of Shadows, etc.)
For all the difficulty that this game presents, the Looplets and Emeras are actually pretty useful. Type Bulldozer and Barrage are SO useful in tough dungeons, especially in ones where you have a type disadvantage.
If your partner faints in a dungeon and you have no Reviver Seeds, YOU DON'T AUTOMATICALLY LOSE! This is amazing, I love this. No longer do I have to be brought down by my partner's incompetence! Similarly to guests you bring on missions.
AI is surprisingly good in this game. Obviously there are some holes; some Pokémon completely forget about Abilities, but overall most Pokémon will go for ranged attacks to avoid approaching you and partners tend to have a very good grasp on when to use ranged attacks and on the type matchup.
In the same vein, the partners generally know how to avoid sleeping Pokémon and traps.
Also, traps break after a single use. This is also very nice.
A lot of dungeon variety.
The plot is...fairly intricate. Perhaps a little weaker than previous installments, but certainly engaging due to how many different aspects there are to it.
The final dungeon is pretty darn cool.
The twist ending at the end was...unexpected, to say in the least. It almost seems to push the bill that the ending will be similar to previous installments with the player returning to the human world, but this time they pull a fast one and change the roles...something I was not expecting at all.

They kept how few spaces around you can see from GtI. I really wish I could see more of the map at times...
The plot, with all of its intricacies, is pretty linear. It doesn't allow for that much deviation.
Those Pokémon who invite you over to their Secret Base and spring a Monster House on you. Screw those guys. Screw you, Houndoom.
Pushing vs. changing spots with your allies is actually a little wonky when first getting used to it.
You level up EXTREMELY SLOWLY and all the Pokémon in the dungeons level up EXTREMELY RAPIDLY. The level curve really needs some adjustments because I keep getting OHKO'd by things that are super-effective and 2HKO'd by moves that are not very effective.
Unless you sell your Gold Bars, money is pretty tough to come by.
Too many dungeons just use rehashed GtI songs, especially Ragged Mountain. Ragged Mountain and its Illusory counterpart get used all over the place...
The addition of a Tiny Reviver Seed and a regular Elixir seemed a little unnecessary, especially considering that the regular Reviver Seed and the Max Elixir aren't any harder to come by.
The trailer got us all hyped for legendaries everywhere but some of them only appeared in those cutscenes that were shown during the trailers, like Lugia, Dialga, Reshiram, and Zekrom. Disappointed that they didn't get to do much of anything, even in the final battle.
After the novelty of the Bittercold final battle, the Dark Matter final battle just seemed like a cop-out. Still a good boss battle, mind you, but not as novel.
The whole idea of deception in the plot feels beat to death. Practically every single character deceives you over something or other, and it gets predictable after a while.
For a Grass-type starter, Yveltal's boss battle is BRUTAL! Oblivion Wing + Dark Aura boosted Dark Pulse is just painful to deal with.
In the post-game, Pokémon being out or "closed" gets a little irritating.
This game has a lot of dungeons, but few are actually memorable. Some of them use remixed versions of old songs or just flat-out use old songs, mostly from GtI, but...only the ones used in the plot are memorable.
The ending also felt like a bit of a cop-out in a bid to make the partner disappear instead of you. It dunks a whole bunch of exposition at the end to justify making the partner disappear as opposed to the player. And from what I can tell of the epilogue, it's just a wild goose chase trying to get the partner back. It's kind of...well, I won't say dumb, but poorly executed.

The ending is definitely quite different than in past games, but here is my own commentary:
The story and dialog is quite well written, but the pacing is little bit of a mess. The school was fun, but the chthonic dungeons in the Voidlands felt a little contrived.
Leveling up doesn't seem to be of much use in this game. You barely gain any stats at each new level.
I much more prefer the Connection Orb with its guaranteed recruitments over the old system of getting lucky with someone's offer. That was particularly horrid with bosses. The bad thing is evolution serves practically no purpose, as you can only acquire one of each Pokémon and evolving would goof that up, and you can't form teams of purely Smeargle. 
The limit of three team members instead of four is a little saddening, but you can get around it with Hoopa.
This game made you REALLY break out the items. I had to carry a selection of wands and Tiny Reviver seeds everywhere. Orbs and non-reviving seeds seem to be decently rare, and Kecleon's shop seems to love selling looplets.
Speaking of looplets, that system is a lot of fun and helps makes each adventure unique. Some emera combinations are quite broken, but it can make the forced nightmarish story dungeons more bearable.