Gonna be honest, it's pretty underwhelming. You get a couple stores that sell new items and a couple food shops that give temporary buffs that you could probably do without entirely, and a mini-game arcade place that lets you play Snake and a non-lewd version of the Labyrinth trials which can be fun... but we're all here because this is a porn game, so it loses its luster very quickly. There's like one shopkeeper you can fuck after spending a ridiculous amount of money at her store, but there doesn't seem to be any other content that I know of. There's a Voltin girl in the arcade who keeps telling you to go away who might have some kind of quest attached to her, and Catherine at the imp store implies she might have sex with you later, but I haven't managed to yet find an option to trigger it with her.
Dark Perpetua's added scenes in her bossfight were probably the biggest glowup of this update though. You can rechallenge her at the end of the Labyrinth gauntlet if you want.