The final book is essentially a random tutorial from pre-existing web content. Avoid them.
They are badly organised and most of their communication happens through Word docs randomly spread over multiple Dropbox folders.
After turning in the review of the first chapter I was told this wasn't the kind of feedback they were looking for. Far as I know, the book was published - factual inaccuracies and all.
The way it worked for me was that they got the first draft of the chapter reviewed by a technical reviewer, and I got the comments. After that, it was all up to me. I chose to fix those mistakes, and some things I chose to ignore. I asked my editor to forward my comments to the technical reviewer, but I doubt that ever happened, since I never heard anything from the reviewer again.
Like it's mentioned in a couple of places in this thread, Packt isn't the best publishing company out there. Their editorial and review standards can be improved a lot, but I'm happy that I got a chance to get my name on a published book because of them.