Greetings,
City of Splendors: Waterdeep is aimed at both the old guard and the new guard. By old guard, I mean anyone with the old products (e.g. RoU1, RoU2, Skullport, the Undermountain trilogy of modules, FR1 - Waterdeep and the North, Volo's Guide to Waterdeep, City of Splendors, etc.) or who purchases such used or as a PDF. New Guard is anyone who wants to run a campaign using just this product.
My intent, and I hope I succeeded, was to aid both the old guard and the new guard. My approach was to hit the highlights of the key stuff, but focus on the new stuff. In other words, City of Splendors (2e) explored the guilds and the noble families in exhaustive detail, but barely touched on the churches. My approach was to cover the guilds and the noble families, but really delve into the churches. That way, if you've got the old stuff, I've told you something new, but if you don't, you've got plenty of material to play with. Another example might be Skullport. This was never intended to be a book about Undermountain, nor could it have. Hopefully, I gave enough info to build your own Skullport if needed, and for those DMs who have access to the 2e Skullport book, I gave a pointer on the little bit of stats that need to be updated. What I did focus on was exploring the other dungeons of Waterdeep, and most of that info is new. (You can find out more about the Dungeon of the Crypt and the Fireplace Level in upcoming issues of Dungeon magazine.)
I also had in mind that this book could be used in at least 3 different ways. One is that it is the base for an adventuring company intent on exploring The North and the Sword Coast.
Two is that it is the basis for a campaign set wholly within the city. And three is that the city is a "teleport in" city.
To explore the third use further, game balance in 3e assumes ready access to 'upgrading' magic' (swapping in +3 plate for +4 plate when you can afford it). Waterdeep can serve a campaign set anywhere in the Realms as a place to teleport in, buy your stuff, and leave. The tables in the beginning of Chapter 1 are designed to facilitate this. They also work for anyone who needs a high level knowledge-like skill check ... teleport in, consult the sage, and get back to the adventure. Of course a good DM knows how to "distract" the would-be quick shopper.
Apologies in advance for the rambling nature of this post,
--Eric