I beat Persona 5 on hard. I'm only going to talk about basic game mechanics and maybe some general plot and first few hours of gameplay here.
The first thing I want to mention is how stylish this game is. Pretty much everyone already knows this from early footage, but it's worth bringing up again as a reminder. Nearly very menu and submenu has a unique animation and it never gets old to watch it transition. The important players from previous Persona titles returned, including composer Shoji Meguro. However Shihoko Hirata, the vocalist from 4, passed the baton to Lyn. It seems like many people loved Persona 4's sound track, but I much prefered Lyn's stylings over Shihoko's here.
I really like 5's aesthetic of literally removing the mask hiding your true self. The process is also similar to Persona 4's approach of "obtaining the facade to face life's hardships", but it's different in one key aspect. The characters in both games are psychologically, and often also physically, backed into a corner, but whereas 4 would have you succumb to societal pressures before eventually accepting your ego, 5 is about being mad as hell and not taking it anymore.
In battle, this time your options are mapped to discrete buttons. When your persona is selected or your gun is drawn, the animation is peformed while you're selecting your target. Once you learn a target's weakness, you can press R1 to scan enemies and automatically select a move that will hit a target's weakness. Post-battle results can take a couple seconds to load you out of battle, but there are also no more mini-games to contend with before you can get back to dungeon crawling. All of this has a net effect of speeding up battles.
I was afraid reintroducing negotiations to Persona would be a step back, but I'm glad I was wrong. The way it's framed as a "Hold up" makes thematic sense and deciding whether you want to negotiate or all-out attack makes engaging in that system actually matter. Persona 5 also makes the smart decision of keeping every correct answer to questions static. Even if you fail a negotiation, you still learned something about their personality and what not to say on your next attempt.
One of my favorite new features is the expansion made to social links in Persona 5. On top of the standard ailment recovery and withstanding lethal blows introduced in 4, 5 goes a bit farther with unique skills for each of your party members. Additionally, non-party member social links offer their own set of perks that drastically aid you in both the combat and life-sim parts of the game.
The last thing I want to mention are the dialogue options. Once again, your dialogue options don't affect story events (for the most part) but they've struck a better tone here than in the past. You're allowed to express doubt over the morality of your actions, play coy when you're questioned, or slyly use double-speak in your responses. This has the effect of making the protagonist feel like more of a character, he even speaks 1% more than previous protagonists!
All in all, I really enjoyed my time with Persona 5. I might write some more about it later, maybe I'll do a spoiler post too.