I'm chairing a panel on this topic in about half an hour. Should be interesting - and it's the first time ever, as far as I recall, that Jenny and I have ended up being on the same panel at a convention.
The panel will be looking at literary issues, such as how realistically science fiction and fantasy writers portray actual or imagined religions. What are good examples and bad examples of this kind of world building. We won't be coming to blows over whether any religion is actually true. Incidentally, Jenny was on a similar panel at a convention last year, and was the only atheist. I think it's all atheists and only one religious person this time. I think most science fiction fans and professionals are atheists, though the picture may be a bit different with fantasy - there are going to be plenty of people who follow Wicca or some other kind of spiritual belief system that falls outside traditional kinds of monotheism.
Anyhow, should be an interesting panel. Later in the day, I'm on a panel about human enhancement technologies - the subject of one the books that I'm currently working on, Humanity Enhanced (to be published by MIT Press).