At point of writing, I am about two hours in, and just doing the first exploration of Tartarus. I played the original Persona 3 long ago during the PSP era, and it was my first Persona game, so I got a soft spot for it (I played the female character tho).

It makes a very big difference being able to traverse everywhere on foot, and seeing everything in full detail and full HD - similar to how I am able to do it in Persona 5 Royal. From my minimal experience so far, it seems like there have been new events and items added in the game that wasn't in the original.