I sort of enjoyed this book, and I sort of didn't.
To preface my impressions of this book, I do agree with most of Hitchens' basic premises. I don't believe in God, and I do agree that religious fanaticism has resulted in plenty of damage to the human race.
Unlike many other atheist writers, Hitchens doesn't discriminate: he includes the Eastern religions (Hinduism and Buddhism, for ex) in his list of religions that have "poisoned everything." I thought that his indictments of Eastern religions were interesting, mostly because I wasn't as aware of how those belief systems have also created problems in the world, since I'm far more familiar with Judeo-Christian religious issues.
The book has some downsides, though, one of which is Hitchens' rambling, ranty writing style. I know that was his stock in trade, but it can get old in a full length book.
My other, main complaint is not with Hitchens book itself, but with the general dearth of inspirational atheist writing. The pantheon of atheist literature seems to be in this vein--intentionally confrontational, bent on tearing down other people's belief systems.
This is Hitchens' (and Dawkins') main point, I think, which is a shame. Hitchens is approaching the subject of religion and belief (or lack thereof) from the perspective of philosophy. He believes that the world would be a better one without religious belief, and he was trying to convince others of that (leaving aside the fact that a book titled "God is Not Great" isn't going to attract many religious readers).
I guess I've had too much anthropology, though, because I don't think religion poisons everything. Sure, it poisons some things, but as an anthropologist, I accept that humans want and need religion. It's here to stay, and that's not a bad thing. I think it's up to thinking people to moderate religious fanaticism, but I don't see any point in railing against something that will continue to exist in our societies.
Where are the inspirational atheist writers?! Don't drag us down into petty mud-slinging wars with religious fundamentalists. Make us feel the awe and power of the mysteries of evolution and the incomprehensibility of the infinity of the universe!