Here are the promised impressions after clearing the game yesterday.
Time to clear: About 105-110 hours on Normal.
Let me preface this by saying that I found both Persona 3 and Persona 4 (and 4G) very tedious, both in and out of dungeons and were never able to put more than 10-20 hours into them.
Thanks to its style, Persona 5 looks really great, low quality textures aside. I honestly don't understand this decision, since they really stick out when everything else looks good. Style aside, it's not a technical masterpiece, but some signs here and there aside, I really liked the look of the whole package.
As for the music, I enjoyed most of the BGMs and would even leave the game running while doing other stuff.
Gameplay-wise, I feel that P5 is a huge step up from P3 and P4 in almost every way.
A ton of changes like being able to see if there are any Social Link (here Cooperations) people in any of the locations, Coops giving you access to a ton of useful passive and active skills, non-randomized story dungeons and other things like that made the game a much better experience.
The social stuff felt much more streamlined, with people texting you when they are free etc. and not being tied to strict schedules as much as in P4, which made the social part much less tedious. If I were to complain about something, it would be high stat requirements for certain socializations and the fact that some of the coop storylines felt a bit one note. Mind you, they were still good, moving stories there, but I think I expected more surprises in them.
Speaking of stories, I really enjoyed the P5 main storyline and didn't find the predictable parts back at all. On the contrary, I was glad that I wasn't in the dark, going from one target to the next for most of the game. The whole thing started and continued to go in a much darker direction than what I was expecting. And while the P4 story sometimes felt more like Twin Peaks, Persona 5 is trying to tackle very real issues present in modern day Japan. I really liked the last stretch of the game and found the story resolution very satisfying.
Regarding the characters, in the end I liked most of them and no one got on my nerves enough to never want them in the party. A part of the cast was a bit to quirky for me, but they all became quite likable at one point or another.
Dungeon wise, I loved what they did with not only making dungeons non random, but also adding puzzles etc. to most of them. While all felt on the easy side, it was a nice change of pace from fighting the same few types of enemies in each dungeon for hours. As for the length, as soon as I got my hands on SP recovering accessories I started doing them all in one in game day whenever possible and aside from a few instances, didn't really feel like they dragged on for too long. 2-4 hours per dungeon, if there's only a few of them in the game isn't so bad in my opinion.
As for the combat, the Baton Touch system allowing you to switch to another party member after getting a One More was great (for saving SP). It really changed the dynamics of battles, making them snappier. That said, I had one problem with it - you had to raise up the coop with each character to a certain level (sometimes unlocking it would be enough) to be able to use Baton Touch with them. If I'm not mistaken, for most new party members this could be only done after finishing the dungeon where they joined you. That made them pretty much useless in my eyes (BT also increases your damage) for that dungeon, which was a bit of a bummer.
One thing regarding the combat I wish they addressed, is having only one animation for each character after the all out attack finisher. Those, while looking great, got old very early on and didn't change for the whole game. Oh, and OHKO skills are still as annoying as they always were in SMT games. At least high level Personas could nullify most of them.
Another feature I loved was the return of demon conversations, one of my favorite parts of SMT games. Here the conversations felt much less random, because each enemy had a specific personality, based on which you knew what type of answers they expect (in theory).
All in all, while the game still had flaws, like some parts dragging for a bit too long etc., during my whole week+ of marathoning it, I never once felt tired of it enough to put it down. All I wanted to do was to keep playing, because each dungeon felt very fresh, and the story was very satisfying from the beginning to the end. Even grinding in the random dungeon didn't feel bad, because the battles felt much faster than in previous games.
I approached P5 very cautiously, because of my experience with P3 and P4, but now after finishing it I can say that I'm glad that I gave it a chance. I think it's one of my favorite games ever and I can't even imagine how good an improved Persona 6 would be.