The second half of the book was better than the first, which seemed a bit repetitive, in fact once the author even says that he is being repetitive-and he's right. The first half of the book is about the importance of cities and the second half is about having a ministry vision for your city.
There are a few times when I felt that in the first half the author stretched to make his point. For example, saying that Jesus' ministry was urban-focused - yet the gospels show Jesus ministering in the villages of Galilee and rarely even going to the nearby Decapolis, which was the urban center of the Galilee region. That doesn't take away from the main thesis of the book, but it seemed like a stretch to try to assert that point.
One big question I felt was never answered is what do they feel differentiates urban from rural - at what point is a city a "city" in the sense they're talking about. Clearly they are writing from an American perspective and assuming that many Christian think in an anti-urban way, which I think is not as much the case as they might think.
Overall though, it's a good book, particularly the second half.