If I understand it correctly, the new book is 1/2 sourcebook on Waterdeep and 1/2 city adventure for levels 1-5.
Wanting to know what all the fuss was about, I picked up the Wayfinder's Guide to Eberron on DDB and totally dig it! My new campaign is going to be set in Khorvaire.
Obvious question - why would I buy Dragon Heist?
To me heist theme is fantastic for Eberron, and I suppose adventure portion could be set in Sharn with some serious changes.
Has WOTC said anything about details included in book to help DM's use in other settings?
Not great value for first part of the book though, aside from cherry picking to flesh out Sharn?
You might want to buy Guildmasters Guide to Ravnica's book too then as it is supposed to have tools in it for running urban campaigns.