Sorry, I definitely did not mean that A level RS is a waste of time. Hell, I'm an 'A' level lecturer in the subject, so I really don't think that!
As for GCSE, I'm sorry, but I do think that compared to other GCSEs it lacks academic rigour. Speaking as a parent, I personally would not advise my child to do it at GCSE, although I would be more than happy for her to study it at 'A' level. I have just found that too many students try doing A level RE thinking it will be easy, like their GCSE was and then get a huge shock. I personally find the jump between GCSE RE and A level RE greater than that of a lot of other subjects. Just my opinion mind!
Also, second the comments RE the Ontological argument - in fact all of them, it is strange that people won't discuss them because of their beliefs. As TS & P said, the OA only works when you are a believer. As for the others, they are also attempts to prove the existence of God, and so I have never found believers (whether Christian or Muslim) to have a problem with them. In fact, many of my Muslim students postively enjoy studying the Kalam (muslim) version of the cosmological argument, and for the Catholics, there's always good old Aquinas to throw in. In 8 years of teaching A level RS, I have never encountered such a problem. Sounds strange to me!!