For example, when he talks about touring the US, he talks about people coming up to him at book signings and thanking him for saying what they were thinking. He doesn't talk about people saying that he opened their eyes.
I have no doubt that the God Delusion convinced at least some people to switch over to atheism, but I suspect that they were limited to people who were already on the fence. I haven't looked at it, but Dawkins also said that his site contains letters from people who have become atheists based on his work. Personally, I think that his evolutionary work makes a better argument than his works about atheism.