Has studying philosophy altered anyone's religious beliefs (example, devout Jew/Muslim/Christian to atheist/agnostic)? Would you recommend intro to philosophy (uni level course) to a religious person?
I'm sure the study of philosophy has altered many people's religious beliefs. In my experience as a both religiously and philosophically inclined person, the "shock" is likely to be greater if your relationship with religion is primarily a case of "received" or unexamined beliefs. If you are already inclined to wrestle deeply with your theological (or other) beliefs, studying philosophy is, in general, less likely to shake your worldview. (Conversely, the study of philosophy can be an equally disruptive experience for someone who comes to it with a dogmatic or unexamined belief in a materialistic-scientific world view).
Of course, there's always the chance you could be highly influenced by some particular philosopher with either an atheistic or a theistic worldview. With that in mind, the atheistic philosophers have been in the ascendancy for quite some time now, but I don't personally foresee that as a permanent trend.
As far as philosophy courses, they are highly instructor-dependent and vary quite widely in terms of content, disposition and quality. It's not unheard of to find one that is openly hostile to religious belief, but even that might not necessarily be a bad place for a religious person solidly grounded in his or her faith --it might leave you better able to understand/defend what you believe in and why.