Apart from general bugfixes and QoL improvements, two biggest additions were a contact list (Call NPCs and they will come join your party if they like you enough) and a large story expansion with cutscenes and new dungeon using original tilesets.
If you want to skip straight to the new dungeon without having to play the game from the start, then go to the village Inn, go to the spot in the picture below and put in the code that is also in the picture.
