To quote Paul, "For I resolved to know nothing while I was with you except Jesus Christ and him crucified" (1 Corinthians 2:2 NIV). That's the stance I try to take. Yes, I know a lot about the Bible, some of the history of Christianity, a good deal about theology and ethics as a whole, and am starting to learn about the early Christians in particular--all of it amounts to nothing in comparison to what is the ultimate truth, that Jesus Christ was crucified to save us.
Oh, and I forgot to mention it earlier, but I agree about Jehova's Witnesses. They are a different religion, really. They claim to know Christ but hold ridiculous beliefs that are contrary to the Bible, one of which being that only 144,000 will be saved, a gross misunderstanding of Revelation 7. Also, they've tried to prophesy the second coming a number of times, neglecting that Jesus said that "No one knows about that day or hour, not even the angels in heaven, nor the Son, but only the Father" (Mark 13:32 NIV). For that reason, I'm not sure I count them as Christians.