My book was designed for programmers who already knew GWT; the negative comments seem to come from people who expected getting to learn GWT from zero, and that wasn't the objective of the book.
The book considers several common problems, and deals with them, sometimes providing several solutions (and some flawed ones are also analyzed). I did go in detail with MVP, UIBinder, and the new GWT 2.0 aspects, but for example I didn't write a single line about common widgets.
Hope this helps!
Great fan of Open Source, Linux, and web development with GWT; all of these come together for my ESSENTIAL GWT book!