Some 100 buses in London are carrying this ad now for some time. Christian activists tried to stop these ads "reasoning" "Advertisements are not allowed to mislead consumers". Luckily the British surveillance agency has not accepted the complain.
The philosopher Stephen Law takes this event as an occasion to point to his essay "Could it be pretty obvious there's no God?"
I was wobbling in all my life after childhood between a more agnostic position and a clear atheistic position.
In the last years I turned back to this atheistic position because philosophers like Russel or Law and Scientists like Stenger ("the comprehensible cosmos") are simply convincing.
Law cites Blaise Pascal: “Let us say: 'Either God is or he is not.' But to which view shall we be inclined? Reason cannot decide this question.“ And then he says: "I reject that view. It seems to me that by observing the world around us, we can answer the question of whether God exists. In fact, I’m going to suggest it’s pretty obvious there’s no God." He then outlines is arguments in http://stephenlaw.blogspot.com/2008/12/could-it-be-pretty-obvious-theres.... An interesting long discussion thread follows.
Also defining myself an atheist I am somewhat concerned about the missionary zeal of some of the "new atheists" like Richard Dawkins and his entourage. I am very much convinced to defend the freedom of non believers against any intrusion from any religion, but I do not see a lot of sense in combating religion. See also Sam Harris hit the point