I do like the diversity. Act 1 is the fun adventuring content in the fun adventuring content environment. Act 2 deals with the divine and their influence over the world - and I do like a bit of horror in this regard. Act 3 is the conclusion and you reach the city. I love the city and how it is made to feel densely populated, but I would have appreciated it much less if it had been all city.
That being said: I keep wondering how much they had originally planned for BG proper. For example I wonder if more roof-content was planned, since most of the roofs have quite a bit of detail and some hidden treasure and you can quite comfortably traverse the city up there - if you can jump far enough or have enough spell slots.
