Necro since I'm playing 7 and I'm pretty pleased with it. After 6 felt like a massive downgrade, 7 is back to form with fixing a ton of issues.
First of all you have a full roster of demons and monsters, no more "everyone is humanoid" bullshit. Your plot NPC roster is pretty small so I still use generics in the story mode. Some generics are also more unique with their abilities, which is nice for more strategic gameplay.
The plot itself is better. You have more complexity in the setting and the cast actually has a part to play in the game rather than tagging along the MC, sadly the MC comes off as very plain and unmemorable.
The gameplay is the usual Disgaea deal, there is no more auto battle (though you can use it on stage replay) and the difficulty is overall very easy, especially if you use the new Nether Hospital gacha system to get some broken gear.
The animations are better, and feel more inline with the old 2D animations.
tl;dr, I'm having fun with it