Dawkins unfortunately can't turn down his snarky tone until the middle of the book, when his very interesting arguments about the biological roots of religious belief begin. While I am already predisposed to his argument, the people he wants to reach aren't going to make it very far into the text thanks to his dismissive prose.
I do agree, though, with his defense that researching religion in the depth that his critics seem to demand is unnecessary considering his approach. He does a good job pointing out the logical inconsistencies of religious arguments (and arguments for God); he does a decent job summarizing the problems with Judeo-Christian morality as presented in the holy books. Then again, isn't Dawkins equally upset with Creationists & ID people who fail to study Darwin before making their critiques? I suspect his defense would be that at least he's using reason to determine why god and religion are faulty. Reason without intense research, that is.
I'm not sure Dawkins wants this book to stand by itself. He continually references other works that deal with ideas he admits are tangential. It seems that readers and critics believe Dawkins should be handling everything himself, but he's part of the scientific community, which bases much of it's research on collaborative efforts. Perhaps with that in mind, his research-shortcomings make more sense.
In the end, the book makes compelling arguments against the necessity of religion and bolsters, in my view, the idea that humans are moral beings without outdated texts to guide them. That, if anything, is the most important topic of discussion and not whether there really is a flying spaghetti monster.