Really, REALLY pretty looking, I love the mixture of 2D & 3D, it took me a while to figure out the background was a model.
I never found any of the ghosts, but I did find an area in the top left of the map (I was taking the different alleyways looking for ghosts) where you can get out of bounds. You can get back in bounds easily, so it wasn't a problem, but might be something to look into.