This review was long pending.
I was the reviewer for Pro SharePoint 2007 Development Techniques.
This book is different than other sharepoint books I have read/reviewed. I can split it amongst two major categories.
Category 1 is Niche topics, such as WSRP, DSL etc as applied to SharePoint. These topics are nearly impossible to find covered anywhere. So if you need coverage on that information, this is where you look.
Category 2 is hardcore SP topics, such as using AJAX in webparts for connections, reporting services + SP, and a deep coverage of search.
I wouldn't recommend this book to someone looking to learn sharepoint. Scot Hilier's book is better suited for that purpose. However, if you are a seasoned SharePoint developer, this book is a decent read.
Full disclaimer: I was the reviewer for this book.