We're both "Bible Believing" Conservative Christians and it adds a great deal to our relationship. We love to talk about God - about what He's doing in our lives - about what He's teaching us, etc. I love it when I catch my husband reading the Bible and He talks about what God is showing him and laying on his heart. Today was so cool because we got to talking about it even and it really gives me a deeper insight into my husband and who he is and why he acts the way he does.
The only time I've ever had a mismatch of religious beliefs affect a relationship was the guy I dated from a Catholic family; his mom thought I was a heathen and therefore shouldn't be dated. However, it still wasn't the reason the relationship didn't work, so meh. Our religious differences never pop up with the current guy.
My SO is an atheist and I'm Christian but it doesn't really interfere with our relationship, our religious beliefs are our own and as long as we don't put each other's beliefs down I don't think it matters
We are both Atheists, but I don't think it would matter much either way - I come from a very catholic family (and I am baptized) went to catholic school, etc, etc. He's also very tolerant of others who are religious, so I feel we'd be okay even if we had differing views on it all.
We used to share the same beliefs, I even switched faiths to marry him. The church has let me down too many times... He still believes, I do not. We live with it and while he misses me by his side Sunday's, understands my reasons.