I've read about 200 pages of The God Delusion. It is well-written and easy to follow. The only real bump in the road is his admission that physics is in need of a little work to provide a more convincing argument against design than is provided by Natural Selection. In the end I think Dawkins is successful in his overall argument. There is simply no good response to the response that God would require more of an explanation than the universe itself.
One thing I took away from the book is his reaction to the 'problem of evil'. He seems unconcerned about it logically, since it can be solved by postulating enemy gods or seeing evil as the result of human free-will. The point of the argument for most monotheists is that God is supposed to be all-powerful and all-good. The problem of evil certainly deals a blow to such a God. Most religious people I know end up uncomfortable with the problem of evil. It convinces many people that there is no God at all since for them they either want to worship this all-powerful, all-good, God or no God at all. The problem with the free-will argument is that you have to explain the evils that have nothing to do with people, like natural disasters.