From what i have played of the app and the ghosts i have unlocked, both from milestones and just by using the sets, i have to say that i'm really liking this. The darker tone to the game (which you not only can see in the designs of characters and sets, but also in the Ghost's information) really makes this a far more unique LEGO theme than the ones before. I kinda wanna start making a list of Ghosts with their character info from the app game.
i mean, stuff like this:Click image to fully see it.
makes me intrigued about LEGO Hidden Side.
Edit: when it comes to that list, i'm already started working on it a little:
Original image from the app.